WinForms XML - Stellar Water Point

Application Setup

Introduction

Hi, for our exercise, we will create a text-based database Windows Forms application. We will use XML to store the records of our database.

Practical Learning: Introducing the Application

Start Microsoft Visual Studio
In the Visual Studion 2022 dialog box, click Create a New Project
In the Create a New Project dialog box, in the languages combo box, select Visual Basic.
In the list of projects templates, click Windows Forms App
Click Next
Change the Project Name to StellarWaterPoint1.
Set the Location to a path of your choice
Click Next
In the Additional Information wizard page, in the Framework combo box, select the highest version (.NET 9.0 (Standard Term Support)
Click Create

The Main Form of the Application

Our application will use a central form to access the other forms. We will use the default form for that purpose.

Practical Learning: Preparing the Central Form of the Application

In the Solution Explorer, right-click Form1.cs and click Rename
Type WaterDistribution (to get WaterDistribution.vb) and press Enter
Read the message on the message box and click Yes
Click the body of the form to make sure it is selected.
In the Properties window, change the following characteristics:
Text: Stellar Water Point
StartPosition: CenterScreen
MaximizeBox: False
Double-click an unoccupied area of the form to generate its Load event

Impliment the event as follows:

Public Class WaterDistribution
    Private Sub Exercise_Load(sender As Object, e As EventArgs) Handles MyBase.Load Handles MyBase.Load
        Rem If the directory for the database doesn't yet exist, create it
        Directory.CreateDirectory("C:\Stellar Water Point1")
    End Sub
End Class

Water Meters

Introduction

Our application will use forms to create water meter records, to view a record of a water meter, to edit or to delete the record of a water meter.

Practical Learning: Introducing Water Meters

To create a folder, in the Solution Explorer, right-click the StellarWaterPoint1 project -> Add -> New Folder
Type WaterMeters as the name of the folder

Displaying Water Meters

To let the user see a list of the water meters in the database, we will use a form equipped with a list view.

Practical Learning: Displaying Water Meters

To create a form, in the Solution Explorer, right-click WaterMeters -> Add -> Form (Windows Forms)...
TFor the Name of the form, type Central
Click Add
In the Toolbox, click the ListView button and click the form
On the form, right-click the list view and click Edit Columns...

Create the columns as follows:

(Name)	Text	Width
colWaterMeterId	Id	40
colMeterNumber	Meter #	150
colMake	Make	300
colModel	Model	150
colMeterSize	Meter Size	150

Click OK

Position and resize the list view on the form as follows:

Control		(Name)	Other Properties
ListView		LvwWaterMeters	FullRowSelect: True GridLines: True View: Details Anchor: Top, Bottom, Left, Right

Doubte-click an unoccupied area of the form to generate its Load event

Change the document as follows:

Imports System.IO
Imports System.Xml

Public Class Central
    Private Sub ShowWaterMeters()
        Dim xdWaterMeters As XmlDocument = New XmlDocument()
        Dim strFileWaterMeters As String = "C:\Stellar Water Point10\WaterMeters.xml"

        If File.Exists(strFileWaterMeters) Then
            Using fsWaterMeters As FileStream = New FileStream(strFileWaterMeters, FileMode.Open,
                                                                 FileAccess.Read, FileShare.Read)

                xdWaterMeters.Load(fsWaterMeters)

                Dim xnlWaterMeters As XmlNodeList = xdWaterMeters.DocumentElement.ChildNodes

                LvwWaterMeters.Items.Clear()

                For Each xnWaterMeter As XmlNode In xnlWaterMeters
                    Dim lviWaterMeter As ListViewItem = New ListViewItem(xnWaterMeter.FirstChild.InnerText)

                    lviWaterMeter.SubItems.Add(xnWaterMeter.FirstChild.NextSibling.InnerText)
                    lviWaterMeter.SubItems.Add(xnWaterMeter.FirstChild.NextSibling.NextSibling.InnerText)
                    lviWaterMeter.SubItems.Add(xnWaterMeter.FirstChild.NextSibling.NextSibling.NextSibling.InnerText)
                    lviWaterMeter.SubItems.Add(xnWaterMeter.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling.InnerText)

                    LvwWaterMeters.Items.Add(lviWaterMeter)
                Next
            End Using
        End If
    End Sub
    
    Private Sub Central_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        ShowWaterMeters()
    End Sub
End Class

In the Solution Explorer, double-click WaterDistribution.cs to display the main form of the application
From the Toolbox, add a button to the form

From the Properties window, change the characteristics of the button as follows:

Control		(Name)	Text	Font
Button		BtnWaterMeters	&Water Meters...	Times New Roman, 24pt, style=Bold

Double-click the &Water Meters button

Impliment the event as follows:

Imports System.IO

Public Class WaterDistribution
    Private Sub Exercise_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        REM If the directory for the database doesn't yet exist, create it
        Directory.CreateDirectory("C:\Stellar Water Point10")
    End Sub

    Private Sub BtnWaterMeters_Click(sender As Object, e As EventArgs) Handles BtnWaterMeters.Click
        Dim Central As Central = New Central()

        Central.ShowDialog()
    End Sub
End Class

A Water Meter Record

Our application will have a list of water meters. A record for each water meter must be created. To make this happen, we will equip the application with an appropriate form.

Practical Learning: Creating a Water Meter Record

To create a form, in the Solution Explorer, right-click the WaterMeters folder -> Add -> Form (Windows Forms)...
For the Name of the file, type Create as the name of the form
Click Add

Design the form as follows:

Stellar Water Point - New Water Meter

Control	(Name)	Text	Other Properties
Label		&Meter #:
MaskedTextBox	MtbMeterNumber		Masked: 000-000-000
Label		M&ake:
TextBox	TxtMake		Modifiers: Public
Label		M&odel:
TextBox	TxtModel		Modifiers: Public
Label		Me&ter Size:
TextBox	TxtMeterSize		Modifiers: Public
Button	BtnOK	&OK	DialogResult: OK
Button	BtnCancel	&Cancel	DialogResult: Cancel

Using the Properties window, change some characteristics of the form as follows:

FormBorderStyle: FixedDialog
Text:            Stellar Water Point - Water Meter Setup
StartPosition:   CenterScreen
AcceptButton:    BtnOK
CancelButton:    BtnCancel

In the Solution Explorer, below the WaterMeters folder, double-click Central.cs
From the Toolbox, add a button to the form below the list view

Change the characteristics of the button as follows:

Control	(Name)	Other Properties
ListView	LvwWaterMeters	FullRowSelect: True GridLines: True View: Details Anchor: Top, Bottom, Left, Right
Button	BtnNewWaterMeter	&New Water Meter... Anchor: Bottom, Right

On the Central form, double-click the New Water Meter button

Implement the event as follows:

Imports System.IO
Imports System.Xml

Public Class Central
    Private Sub ShowWaterMeters()
        REM Create a reference to the XML's DOM object
        Dim xdWaterMeters As XmlDocument = New XmlDocument()
        REM Indicate the file that holds a list of water meters
        Dim strFileWaterMeters As String = "C:\Stellar Water Point10\WaterMeters.xml"

        REM Check whether a file that holds a list of water meters exists
        If File.Exists(strFileWaterMeters) Then
            REM If that file exists, open it
            Using fsWaterMeters As FileStream = New FileStream(strFileWaterMeters, FileMode.Open,
                                                                 FileAccess.Read, FileShare.Read)

                REM Get the list of water meters from the file and store
                REM the records in the previously created DOM object.
                xdWaterMeters.Load(fsWaterMeters)

                REM If there is at least one record for the water meters, 
                REM create an XmlNodeList list and transmit it to 
                REM a collection that wille be used in the view page.
                Dim xnlWaterMeters As XmlNodeList = xdWaterMeters.DocumentElement.ChildNodes

                LvwWaterMeters.Items.Clear()

                For Each xnWaterMeter As XmlNode In xnlWaterMeters
                    Dim lviWaterMeter As ListViewItem = New ListViewItem(xnWaterMeter.FirstChild.InnerText)

                    lviWaterMeter.SubItems.Add(xnWaterMeter.FirstChild.NextSibling.InnerText)
                    lviWaterMeter.SubItems.Add(xnWaterMeter.FirstChild.NextSibling.NextSibling.InnerText)
                    lviWaterMeter.SubItems.Add(xnWaterMeter.FirstChild.NextSibling.NextSibling.NextSibling.InnerText)
                    lviWaterMeter.SubItems.Add(xnWaterMeter.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling.InnerText)

                    LvwWaterMeters.Items.Add(lviWaterMeter)
                Next
            End Using
        End If
    End Sub
    
    Private Sub Central_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        ShowWaterMeters()
    End Sub

    Private Sub BtnNewWaterMeter_Click(sender As Object, e As EventArgs) Handles BtnNewWaterMeter.Click
        Dim wm = New Create
        Dim fiWaterMeters As FileInfo = Nothing
        Dim xdWaterMeters = New XmlDocument
        Dim strWaterMeters = "C:\Stellar Water Point10\WaterMeters.xml"
 
        If wm.ShowDialog = DialogResult.OK Then
            fiWaterMeters = New FileInfo(strWaterMeters)

            If fiWaterMeters.Exists Then
                Using fsWaterMeters = New FileStream(fiWaterMeters.FullName, FileMode.Open,
                                                          FileAccess.Read, FileShare.Read)

                    xdWaterMeters.Load(fsWaterMeters)
                End Using
            Else
                Using fsWaterMeters = New FileStream(fiWaterMeters.FullName, FileMode.Create,
                                                          FileAccess.Write, FileShare.Write)

                    xdWaterMeters.LoadXml("<?xml version=""1.0"" encoding=""utf-8""?>" +
                                                  "<water-meters></water-meters>")
                    xdWaterMeters.Save(fsWaterMeters)
                End Using
            End If
        End If

        Using fsWaterMeters = New FileStream(fiWaterMeters.FullName, FileMode.OpenOrCreate,
                                              FileAccess.ReadWrite, FileShare.ReadWrite)

            Dim xeWaterMeter = xdWaterMeters.CreateElement("water-meter")

            xeWaterMeter.InnerXml = "<water-meter-id>" + wm.TxtWaterMeterId.Text + "</water-meter-id>" +
                                    "<meter-number>" + wm.MtbMeterNumber.Text + "</meter-number>" +
                                    "<make>" + wm.TxtMake.Text + "</make>" +
                                    "<model>" + wm.TxtModel.Text + "</model>" +
                                    "<meter-size>" + wm.TxtMeterSize.Text + "</meter-size>"
            
            xdWaterMeters.DocumentElement.AppendChild(xeWaterMeter)
            xdWaterMeters.Save(fsWaterMeters)
        End Using

        ShowWaterMeters()
    End Sub
End Class

To execute the application, on the main menu, click Debug -> Start Without Debugging
On the Central form, click the Water Meters button:
Click the New Water Meter button:

Enter the value for each of the following records and click OK (or press Enter) for each:

Meter #	Make	Model	Meter Size
392-494-572	Constance Technologies	TG-4822	5/8 Inches
938-705-869	Stan Wood	66-G	1 Inch
588-279-663	Estellano	NCF-226	3/4 Inches

Close the forms and return to your programming environment

Water Meter Details

Sometimes, a user may want to check the values of a water meter record. To support this, we will add an appropriate form to our application.

Practical Learning: Creating a Water Meter Record

To create a form, in the Solution Explorer, right-click WaterMeters -> Add -> Form (Windows Forms)...
For the Name of the form, type Details
Press Enter
Resize the Editor form to have the same size as the Create form
Copy everything from the Create form and paste it in the Editor form
Delete the bottom two buttons and add a new button

Change the design of the form as follows:

Stellar Water Point - New Water Meter

Control	(Name)	Text
Button	BtnFindWateMeter	&Find Water Meter
Button	BtnClose	&Close

On the form, double-click the Find Water Meter button

Implement the event as follows:

Imports System.IO
Imports System.Xml

Public Class Details
    Private Sub BtnFindWateMeter_Click(sender As Object, e As EventArgs) Handles BtnFindWaterMeter.Click
        If String.IsNullOrEmpty(MtbMeterNumber.Text) Then
            MsgBox("You must type a meter number and then click the Find button.",
                                "Stellar Water Point", MsgBoxStyle.OkOnly Or MsgBoxStyle.Information)
            Exit Sub
        End If

        Dim xdWaterMeters As XmlDocument = New XmlDocument()
        Dim strWaterMeters As String = "C:\Stellar Water Point10\WaterMeters.xml"
        Dim fiWaterMeters As FileInfo = New FileInfo(strWaterMeters)

        If fiWaterMeters.Exists Then
            Using fsWaterMeters As FileStream = New FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read)
                xdWaterMeters.Load(fsWaterMeters)
                Dim xnlWaterMeters As XmlNodeList = xdWaterMeters.DocumentElement.SelectNodes("//meter-number[.='" + MtbMeterNumber.Text + "']")

                For Each xnWaterMeter As XmlNode In xnlWaterMeters
                    TxtWaterMeterId.Text = xnWaterMeter.PreviousSibling.InnerText
                    TxtMake.Text = xnWaterMeter.NextSibling.InnerText
                    TxtModel.Text = xnWaterMeter.NextSibling.NextSibling.InnerText
                    TxtMeterSize.Text = xnWaterMeter.NextSibling.NextSibling.NextSibling.InnerText
                Next
            End Using
        End If
    End Sub
End Class

Return to the form and double-click the Close button

Implement the event as follows:

Imports System.IO
Imports System.Xml

Public Class Details
    Private Sub BtnFindWateMeter_Click(sender As Object, e As EventArgs) Handles BtnFindWaterMeter.Click
        REM If the user clicks the Find button, 
        REM make sure there Is a meter number in the top text box.
        If String.IsNullOrEmpty(MtbMeterNumber.Text) Then
            REM If the user didn't type a meter number, 
            REM display a message box to inform the user.
            MsgBox("You must type a meter number and then click the Find button.",
                                "Stellar Water Point", MsgBoxStyle.OkOnly Or MsgBoxStyle.Information)
            REM If the user didn't type a meter number but clicked Find, don't do anything
            Exit Sub
        End If

        REM We will need a reference to an XML Dom object as an XmlDocument variable
        Dim xdWaterMeters As XmlDocument = New XmlDocument()
        REM This is the name and path of the file that holds the records of water meters
        Dim strWaterMeters As String = "C:\Stellar Water Point10\WaterMeters.xml"
        REM We will process the file of water meters using a FileInfo object
        Dim fiWaterMeters As FileInfo = New FileInfo(strWaterMeters)

        REM We need to find out whether a file for water meters was previously created.
        If fiWaterMeters.Exists Then
            REM If that file exists, create a stream of it. Open that file with a read-only status
            Using fsWaterMeters As FileStream = New FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read)
                REM Get the list of water meter records and put those records in the XML Dom object created earlier.
                xdWaterMeters.Load(fsWaterMeters)
                REM Use XPath to locate the water meter that has 
                REM the same meter number as the one in the Meter # text box.
                REM Store the water meter in an XmlNodeList variable.
                Dim xnlWaterMeters As XmlNodeList = xdWaterMeters.DocumentElement.SelectNodes("//meter-number[.='" + MtbMeterNumber.Text + "']")

                REM If there Is a water meter in the database with 
                REM the number that the user typed, locate that water meter 
                REM and display each of its values in the appropriate text box.
                For Each xnWaterMeter As XmlNode In xnlWaterMeters
                    TxtWaterMeterId.Text = xnWaterMeter.PreviousSibling.InnerText
                    TxtMake.Text = xnWaterMeter.NextSibling.InnerText
                    TxtModel.Text = xnWaterMeter.NextSibling.NextSibling.InnerText
                    TxtMeterSize.Text = xnWaterMeter.NextSibling.NextSibling.NextSibling.InnerText
                Next
            End Using
        End If
    End Sub

    Private Sub BtnClose_Click(sender As Object, e As EventArgs) Handles BtnClose.Click
        Close()
    End Sub
End Class

In the Solution Explorer, below the WaterMeters folder, double-click Central.cs to open its form
From the Toolbox, add a button to the form below the list view and to the right of the New Water Meter button

Change the characteristics of the button as follows:

Control	(Name)	Other Properties
ListView	LvwWaterMeters	No Change
Button	BtnNewWaterMeter	&New Water Meter... Anchor: Bottom, Right
Button	BtnViewWaterMeter	&View Water Meter... Anchor: Bottom, Right

Double-click the View Water Meter button

Change the document as follows:

Imports System.IO
Imports System.Xml

Public Class Central
    Private Sub ShowWaterMeters()
        . . .
    End Sub
    Private Sub Central_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        ShowWaterMeters()
    End Sub

    Private Sub BtnNewWaterMeter_Click(sender As Object, e As EventArgs) Handles BtnNewWaterMeter.Click
        . . .
    End Sub

    Private Sub BtnWaterMeterDetails_Click(sender As Object, e As EventArgs) Handles BtnWaterMeterDetails.Click
        Dim waterMeterDetails As Details = New Details()

        waterMeterDetails.Show()
    End Sub
End Class

To execute the application, on the main menu, click Debug -> Start Without Debugging
On the Water Distribution form, click the Water Meters button
On the Central form of water meters, click the View Water Meter button:
In the Meter # text, type 392-494-572
Click the Find button:
Close the Details form
On the Water Meters form, double-click the third record
Close the forms and return to your programming environment

Updating a Water Meter Details

One of the routine operations performed on a database is to change the details of a record. To support this operation for a water meter, we will create a form that can be used to update the information of a water meter.

Practical Learning: Updating a Water Meter

To create a form, in the Solution Explorer, right-click WaterMeters -> Add -> Form (Windows Forms)...
For the Name of the file, type Editor as the name of the form
Click Add
Resize the Editor form to have the same size as the Details form
Copy everything from the Details form and paste it in the Editor form

Change the design of the form as follows:

Stellar Water Point - New Water Meter

Control		(Name)	Text
Button		BtnUpdateWateMeter	&Update Water Meter

On the form, double-click the Find button

Change the document as follows:

Imports System.IO
Imports System.Xml

Public Class Editor
    Private Sub BtnFindWaterMeter_Click(sender As Object, e As EventArgs) Handles BtnFindWaterMeter.Click
        If String.IsNullOrEmpty(MtbMeterNumber.Text) Then
            MsgBox("You must type a meter number and then click the Find button.",
            MsgBoxStyle.OkOnly Or MsgBoxStyle.Information,
                                "Stellar Water Point")
            Exit Sub
        End If

        Dim xdWaterMeters As XmlDocument = New XmlDocument()
        Dim strWaterMeters As String = "C:\Stellar Water Point10\WaterMeters.xml"
        Dim fiWaterMeters As FileInfo = New FileInfo(strWaterMeters)

        If fiWaterMeters.Exists Then
            Using fsWaterMeters As FileStream = New FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read)
                xdWaterMeters.Load(fsWaterMeters)
                Dim xnlWaterMeters As XmlNodeList = xdWaterMeters.DocumentElement.SelectNodes("//meter-number[.='" + MtbMeterNumber.Text + "']")

                For Each xnWaterMeter As XmlNode In xnlWaterMeters
                    TxtWaterMeterId.Text = xnWaterMeter.PreviousSibling.InnerText
                    TxtMake.Text = xnWaterMeter.NextSibling.InnerText
                    TxtModel.Text = xnWaterMeter.NextSibling.NextSibling.InnerText
                    TxtMeterSize.Text = xnWaterMeter.NextSibling.NextSibling.NextSibling.InnerText
                Next
            End Using
        End If
    End Sub
End Class

Return to the form and double-click the Update Water Meter button

Change the document as follows:

Imports System.IO
Imports System.Xml

Public Class Editor
    Private Sub BtnFindWaterMeter_Click(sender As Object, e As EventArgs) Handles BtnFindWaterMeter.Click
        . . .
    End Sub

    Private Sub BtnUpdateWateMeter_Click(sender As Object, e As EventArgs) Handles BtnUpdateWateMeter.Click
        Dim xdWaterMeters As XmlDocument = New XmlDocument()
        Dim strWaterMeters As String = "C:\Stellar Water Point10\WaterMeters.xml"

        Dim fiWaterMeters As FileInfo = New FileInfo(strWaterMeters)

        If fiWaterMeters.Exists Then
            Using fsWaterMeters As FileStream = New FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read)

                xdWaterMeters.Load(fsWaterMeters)
                Dim xnlWaterMeters As XmlNodeList = xdWaterMeters.DocumentElement.SelectNodes("//meter-number[.='" + MtbMeterNumber.Text + "']")

                For Each xnWaterMeter As XmlNode In xnlWaterMeters
                    xnWaterMeter.ParentNode.InnerXml = "<water-meter-id>" + TxtWaterMeterId.Text + "</water-meter-id>" +
                                    "<meter-number>" + MtbMeterNumber.Text + "</meter-number>" +
                                    "<make>" + TxtMake.Text + "</make>" +
                                    "<model>" + TxtModel.Text + "</model>" +
                                    "<meter-size>" + TxtMeterSize.Text + "</meter-size>"
                Next
            End Using

            Using fsWaterMeters As FileStream = New FileStream(fiWaterMeters.FullName, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.ReadWrite)
                xdWaterMeters.Save(fsWaterMeters)
            End Using
        End If

        Close()
    End Sub
End Class

Return to the form and double-click the Close button

Change the document as follows:

import System.Xml

namespace StellarWaterPoint1.WaterMeters

    public partial class Editor : Form
    
        public Editor()
        
            InitializeComponent()
        }

        private sub BtnFindWateMeter_Click(sender As Object, e As EventArgs)
        
            rem If the user clicks the Find button, 
            rem make sure there is a meter number in the top text box.
            if string.IsNullOrEmpty(MtbMeterNumber.Text))
            
                rem If the user didn't type a meter number, 
                rem display a message box to inform the user.
                MsgBox("You must type a meter number and then click the Find button.",
                MsgBoxStyle.OkOnly Or MsgBoxStyle.Information,
                                "Stellar Water Point")
                rem If the user didn't type a meter number but clicked Find, don't do anything
                Exit Sub
            end if

            rem We will need a reference to an XML Dom object as an XmlDocument variable
            dim xdWaterMeters as XmlDocument = new XmlDocument()
            rem This is the name and path of the file that holds the records of water meters
            dim strWaterMeters as string= "C:\Stellar Water Point1\WaterMeters.xml"
            rem We will process the file of water meters using a FileInfo object
            dim fiWaterMeters as FileInfo= new FileInfo(strWaterMeters)

            rem We need to find out whether a file for water meters was previously created.
            if fiWaterMeters.Exists)
            
                rem If that file exists, create a stream of it. Open that file with a read-only status
                using  fsWaterMeters as FileStream= new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                
                    rem Get the list of water meter records 
rem and put those records in the XML Dom object created earlier.
                    xdWaterMeters.Load(fsWaterMeters)
                    rem Use XPath to locate the water meter that has 
rem the same meter number as the one in the Meter # text box.
rem Store the water meter in an XmlNodeList variable.
                    dim xnlWaterMeters  as XmlNodeList = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + MtbMeterNumber.Text + "']")!;

                    rem If there is a water meter in the database with 
rem the number that the user typed, locate that water meter 
rem and display each of its values in the appropriate text box.
                    for each xnWaterMeter  as XmlNode in xnlWaterMeters)
                        TxtMake.Text = xnWaterMeter.NextSibling.InnerText
                        TxtModel.Text = xnWaterMeter.NextSibling.NextSibling.InnerText
                        TxtMeterSize.Text = xnWaterMeter.NextSibling.NextSibling.NextSibling.InnerText
                    next
                end using
            end if
        end sub

        private sub BtnUpdateWaterMeter_Click(sender As Object, e As EventArgs)
        
            rem We will need a reference to an XML Dom object as an XmlDocument variable
            dim xdWaterMeters as XmlDocument = new()
            rem This is the name and path of the file that holds the records of water meters
            dim strWaterMeters as string= "C:\Stellar Water Point1\WaterMeters.xml"
            rem We will process the file of water meters using a FileInfo object
            dim fiWaterMeters as FileInfo= new(strWaterMeters)

            rem We need to find out whether a file for water meters was previously created.
            if fiWaterMeters.Exists)
            
                rem If that file exists, create a stream of it. Open that file with a read-only status
                using  fsWaterMeters as FileStream= new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                
                    rem Get the list of water meter records 
rem and put those records in the XML Dom object created earlier.
                    xdWaterMeters.Load(fsWaterMeters)
                    rem Use XPath to locate the water meter that has 
rem the same meter number as the one in the Meter # text box.
rem Store the water meter in an XmlNodeList variable.
                    dim xnlWaterMeters  as XmlNodeList = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + MtbMeterNumber.Text + "']")!;

                    rem Check each record of the water meters.
                    for each xnWaterMeter  as XmlNode in xnlWaterMeters)
                    
                        rem If you find a record whose water meter is 
    rem the same as the meter number that the user typed,
    rem change the values of the Make, the Model, 
    rem and the Meter Size based on the values 
    rem the user typed in the corresponding text boxes.
                        xnWaterMeter.ParentNode!.InnerXml = "<meter-number>" + MtbMeterNumber.Text + "</meter-number>" +
                                                            "<make>" + TxtMake.Text + "</make>" +
                                                            "<model>" + TxtModel.Text + "</model>" +
                                                            "<meter-size>" + TxtMeterSize.Text + "</meter-size>"
                    next
                end using

                rem Now that a water meter has been changed/update 
                rem (and the file of water meters has changed), save the new version of the file.
                using  fsWaterMeters as FileStream= new FileStream(fiWaterMeters.FullName, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.ReadWrite))
                    xdWaterMeters.Save(fsWaterMeters)
                end using
            end if

            rem If the user has updated a record, we will assume that, 
            rem in most cases (such as usually in real life), 
            rem a user updates one record and moves to other activities.
            rem For this record, after the user has updated a record, 
            rem we will clode the form.
            Close()
        end sub

        private sub BtnClose_Click(sender As Object, e As EventArgs)
            Close()
        end usb
    }
}

In the Solution Explorer, below the WaterMeters folder, double-click Central.cs
From the Toolbox, add a button to the form below the list view and on the right side of the View Water Meter button

Change the characteristics of the button as follows:

Control	(Name)	Other Properties
ListView	LvwWaterMeters	FullRowSelect: True GridLines: True View: Details Anchor: Top, Bottom, Left, Right
Button	BtnNewWaterMeter	&New Water Meter... Anchor: Bottom, Right
Button	BtnViewWaterMeter	&View Water Meter... Anchor: Bottom, Right
Button	BtnEditWaterMeter	&Edit Water Meter... Anchor: Bottom, Right

Display the Central form of the WaterMeters folder
Double-click the Update Water Meter button

Change the document as follows:

import System.Xml

namespace StellarWaterPoint1.WaterMeters

    public partial class Central : Form
    
        public Central()
        
            InitializeComponent()
        }

        private sub ShowWaterMeters()
        
            . . .
        }

        private sub Central_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        
            rem When the open opens, make an attempt to display a list of water meters.
            ShowWaterMeters()
        }

        private sub BtnNewWaterMeter_Click(sender As Object, e As EventArgs)
        
            . . .
        }

        private sub BtnViewWaterMeter_Click(sender As Object, e As EventArgs)
        
            . . .
        }

        private sub BtnEditWaterMeter_Click(sender As Object, e As EventArgs)
        
            rem Get a reference to the dialog box that is used 
            rem to update the details of a water meter.
            Editor editor = new()
            rem Display that dialog box
            editor.ShowDialog()

            rem After using the dialog box, make an attempt to display the list of water meters.
            ShowWaterMeters()
        }
    }
}

To execute the application, on the main menu, click Debug -> Start Without Debugging
On the Central form, click the Water Meters button
Click the Edit Water Meter button:
In the Meter # text, type 938-705-869
Click the Find button

Change the values as follows:

Make:	Stanford Trend
Model:	266G
Meter Size:	1 1/2 Inches

Stellar Water Point - New Water Meter

Click the Update button:
Close the forms and return to your programming environment

Removing a Water Meter from the Database

If a water meter has become useless and you want to make sure it is no more available for customer use, you can delete its record. To assist the user, we will create a form for that operation.

Practical Learning: Deleting a Water Meter Record

To create a form, in the Solution Explorer, right-click WaterMeters -> Add -> Form(Windows Forms)...
In the Name text box, replace the string with Delete as the name of the form
Press Enter
Resize the Delete form to have the same size as the Editor form
Copy everything from the Editor form and paste it in the Delete form

Change the bottom button as follows:

Stellar Water Point - New Water Meter

Control		(Name)	Text
Button		BtnDeleteWateMeter	&Delete Water Meter

On the form, double-click the Find Water Meter button

Change the document as tollows:

import System.Xml

namespace StellarWaterPoint1.WaterMeters

    public partial class Delete : Form
    
        public Delete()
        
            InitializeComponent()
        }

        private sub BtnFind_Click(sender As Object, e As EventArgs)
        
            dim xdWaterMeters as XmlDocument = new XmlDocument()
            dim strWaterMeters as string= "C:\Stellar Water Point1\WaterMeters.xml"

            dim fiWaterMeters as FileInfo= new FileInfo(strWaterMeters)

            if fiWaterMeters.Exists)
                using  fsWaterMeters as FileStream= new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                
                    xdWaterMeters.Load(fsWaterMeters)
                    dim xnlWaterMeters  as XmlNodeList = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + MtbMeterNumber.Text + "']")!;

                    for each xnWaterMeter  as XmlNode in xnlWaterMeters)
                        TxtMake.Text = xnWaterMeter.NextSibling.InnerText
                        TxtModel.Text = xnWaterMeter.NextSibling.NextSibling.InnerText
                        TxtMeterSize.Text = xnWaterMeter.NextSibling.NextSibling.NextSibling.InnerText
                    next
                end using
            end if
        end sub
    }
}

Return to the form and double-click the Delete Water Meter button

Change the document as tollows:

import System.Xml

namespace StellarWaterPoint1.WaterMeters

    public partial class Delete : Form
    
        public Delete()
        
            InitializeComponent()
        }

        . . .

        private sub BtnDeleteWaterMeter_Click(sender As Object, e As EventArgs)
        
            dim xdWaterMeters as XmlDocument = new XmlDocument()
            dim strWaterMeters as string= "C:\Stellar Water Point1\WaterMeters.xml"

            if string.IsNullOrEmpty(MtbMeterNumber.Text)
                MsgBox("You must type a water meter number if you want to delete one.",
                MsgBoxStyle.OkOnly Or MsgBoxStyle.Information,
                                "Stellar Water Point")
                Exit Sub
            end if

            if File.Exists(strWaterMeters) = false
                MsgBox("There is no file for the water meters in the system.",
                                MsgBoxStyle.OkOnly Or MsgBoxStyle.Information,
                                "Stellar Water Point")
                Exit Sub
            end if

            xdWaterMeters.Load(strWaterMeters)

            dim xnlWaterMeters  as XmlNodeList = xdWaterMeters.DocumentElement!.GetElementsByTagName("meter-number")

            for each xnWaterMeter  as XmlNode in xnlWaterMeters)
            
                if xnWaterMeter.InnerText=MtbMeterNumber.Text)
                
                    if MsgBox("Are you sure you want to delete this water meter record from the system?",
                                    MessageBoxButtons.YesNo, MessageBoxIcon.Question,
                                    "Stellar Water Point") =MsgBoxResult.Yes)
                    
                        xdWaterMeters.DocumentElement.RemoveChild(xnWaterMeter.ParentNode!)
                        Exit For
                    end if
                end if
            next

            xdWaterMeters.Save(strWaterMeters)

            Close()
        end sub
    }
}

Return to the form and double-click the Close button

Change the document as tollows:

import System.Xml

namespace StellarWaterPoint1.WaterMeters

    public partial class Delete : Form
    
        public Delete()
        
            InitializeComponent()
        }

        private sub BtnFindWateMeter_Click(sender As Object, e As EventArgs)
        
            rem If the user clicks the Find button, 
            rem make sure there is a meter number in the top text box.
            if string.IsNullOrEmpty(MtbMeterNumber.Text))
            
                rem If the user didn't type a meter number, 
                rem display a message box to inform the user.
                MsgBox("You must type a meter number and then click the Find button.",
                MsgBoxStyle.OkOnly Or MsgBoxStyle.Information,
                                "Stellar Water Point")
                rem If the user didn't type a meter number but clicked Find, don't do anything
                Exit Sub
            }

            rem We will need a reference to an XML Dom object as an XmlDocument variable
            dim xdWaterMeters as XmlDocument = new XmlDocument()
            rem This is the name and path of the file that holds the records of water meters
            dim strWaterMeters as string= "C:\Stellar Water Point1\WaterMeters.xml"
            rem We will process the file of water meters using a FileInfo object
            dim fiWaterMeters as FileInfo= new FileInfo(strWaterMeters)

            rem We need to find out whether a file for water meters was previously created.
            if fiWaterMeters.Exists)
            
                rem If that file exists, create a stream of it. Open that file with a read-only status
                using  fsWaterMeters as FileStream= new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                
                    rem Get the list of water meter records 
rem and put those records in the XML Dom object created earlier.
                    xdWaterMeters.Load(fsWaterMeters)
                    rem Use XPath to locate the water meter that has 
rem the same meter number as the one in the Meter # text box.
rem Store the water meter in an XmlNodeList variable.
                    dim xnlWaterMeters  as XmlNodeList = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + MtbMeterNumber.Text + "']")!;

                    rem If there is a water meter in the database with 
rem the number that the user typed, locate that water meter 
rem and display each of its values in the appropriate text box.
                    for each xnWaterMeter  as XmlNode in xnlWaterMeters)
                    
                        TxtMake.Text = xnWaterMeter.NextSibling.InnerText
                        TxtModel.Text = xnWaterMeter.NextSibling.NextSibling.InnerText
                        TxtMeterSize.Text = xnWaterMeter.NextSibling.NextSibling.NextSibling.InnerText
                    }
                }
            }
        }

        private sub BtnDeleteWaterMeter_Click(sender As Object, e As EventArgs)
        
            rem If the user clicks the Delete button, make sure that 
            rem the right text box contains a meter number
            if string.IsNullOrEmpty(MtbMeterNumber.Text))
            
                rem If the user didn't provide a meter number, display a message box ...
                MsgBox("You must type a water meter number if you want to delete one.", 
                MsgBoxStyle.OkOnly Or MsgBoxStyle.Information,
                                "Stellar Water Point")
                rem .. and stop the operation.
                Exit Sub
            }

            rem Create an XML Dom object
            dim xdWaterMeters as XmlDocument = new XmlDocument()
            rem Get the file that holds a list of water meters
            rem and assign that file to a string variable.
            dim strWaterMeters as string= "C:\Stellar Water Point1\WaterMeters.xml"

            rem If the user provided a meter number and clicked the Find button,
            rem check whether a file for water meters was previously created.
            if !File.Exists(strWaterMeters))
            
                rem If a file for water meters was not created already, display a message box...
                MsgBox("There is no file for the water meters in the system.",
                                MsgBoxStyle.OkOnly Or MsgBoxStyle.Information,
                                "Stellar Water Point")
                rem .. and stop the operation.
                Exit Sub
            }

            rem Since a file of water meters exists, open it.
            rem Store the list of water meters in the XML Dom object that was previously created.
            xdWaterMeters.Load(strWaterMeters)

            rem From the list of XML elements, get a list of elements based one named meter-number.
            dim xnlWaterMeters  as XmlNodeList = xdWaterMeters.DocumentElement!.GetElementsByTagName("meter-number")

            rem Visit each XML node from the list
            for each xnWaterMeter  as XmlNode in xnlWaterMeters)
            
                rem When you get to an element, check whether its meter number is 
                rem the same number the user had typed.
                if xnWaterMeter.InnerText=MtbMeterNumber.Text)
                
                    rem If you find that meter number, enquire from 
rem the user if the water meter must be deleted. 
rem To get that information, display a message box with a Yes and a No buttons.
                    if MsgBox("Are you sure you want to delete this water meter record from the system?",
                                    MessageBoxButtons.YesNo, MessageBoxIcon.Question,
                                    "Stellar Water Point") =MsgBoxResult.Yes)
                    
                        rem If the user had clicked Yes, delete the water meter.
                        xdWaterMeters.DocumentElement.RemoveChild(xnWaterMeter.ParentNode!)
                        Exit For
                    }
                }
            }

            rem Since the list of water meters has been changed, save its new version
            xdWaterMeters.Save(strWaterMeters)

            rem After the deletion operation, close the dialog box and
            rem return to the Central form of water meters.
            Close()
        }

        private sub BtnClose_Click(sender As Object, e As EventArgs)
        
            Close()
        }
    }
}

In the Solution Explorer, below the WaterMeters folder, double-click Central.cs
From the Toolbox, add two buttons to the form below the list view and on the right side of the Edit Water Meter button

Change the characteristics of the new buttons as follows:

Control	(Name)	Other Properties
ListView	LvwWaterMeters	FullRowSelect: True GridLines: True View: Details Anchor: Top, Bottom, Left, Right
Button	BtnDeleteWateMeter	&Delete Water Meter... Anchor: Bottom, Right
Button	BtnClose	&Close Anchor: Bottom, Right

In the Solution Explorer, below WaterMeters, double-click Central.cs to open its form
Double-click the Delete Water Meter button
Return to the Central form of the water meters and double-click the Close button

Change the document as follows:

import System.Xml

namespace StellarWaterPoint1.WaterMeters

    public partial class Central : Form
    
        public Central()
        
            InitializeComponent()
        }

        private sub ShowWaterMeters()
        
            rem Create an XML Dom reference
            dim xdWaterMeters as XmlDocument = new XmlDocument()
            rem Declare a string variable to have the file that holds a list of water meters
            dim strWaterMeters as string= "C:\Stellar Water Point1\WaterMeters.xml"

            rem Create a FileInfo object that holds a reference to the file of water meters
            dim fiWaterMeters as FileInfo= new FileInfo(strWaterMeters)

            rem If you are about to display a list of water meters, first empty the list view
            lvwWaterMeters.Items.Clear()

            rem Check whether a file for water meters was previously created.
            if fiWaterMeters.Exists)
            
                rem If such a file exists, create a Stream for it
                using  fsWaterMeters as FileStream= new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                
                    rem Store the stream of water meters into the XML Dom that was created earlier
                    xdWaterMeters.Load(fsWaterMeters)
                    rem Get a list of the water meter elements from the XML Dom object
                    dim xnlWaterMeters  as XmlNodeList = xdWaterMeters.DocumentElement!.ChildNodes;

                    int i = 1;

                    rem Check each water meter
                    for each xnWaterMeter  as XmlNode in xnlWaterMeters)
                    
                        rem Create a list view item to hold a record of a water meter
                        dim lviWaterMeter as ListViewItem = new ListViewItem(i.ToString())

                        lviWaterMeter.SubItems.Add(xnWaterMeter.FirstChild!.InnerText)
                        lviWaterMeter.SubItems.Add(xnWaterMeter.FirstChild.NextSibling!.InnerText)
                        lviWaterMeter.SubItems.Add(xnWaterMeter.FirstChild.NextSibling.NextSibling!.InnerText)
                        lviWaterMeter.SubItems.Add(xnWaterMeter.FirstChild.NextSibling.NextSibling.NextSibling!.InnerText)

                        rem Pass the list view item to the list view object on the form
                        lvwWaterMeters.Items.Add(lviWaterMeter)

                        i++;
                    }
                }
            }
        }

        private sub Central_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        
            rem When the open opens, make an attempt to display a list of water meters.
            ShowWaterMeters()
        }

        private sub BtnNewWaterMeter_Click(sender As Object, e As EventArgs)
        
            rem Get a reference to the form used to add a water meter
            Create wm = new()
            rem Create a FileInfo object
            dim fiWaterMeters as FileInfo= nothing
            rem Create a file stream object
            FileStream? fsWaterMeters = nothing
            rem Create an XML Dom object
            dim xdWaterMeters as XmlDocument = new XmlDocument()
            rem Declare a string for a file to hold a list of water meters
            dim strWaterMeters as string= "C:\Stellar Water Point1\WaterMeters.xml"

            rem Display the form used to create a water meter. 
            rem If the user finishes using that form and click the OK button...
            if wm.ShowDialog() =MsgBoxResult.OK)
            
                rem Store the file of water meters into the FileInfo object that was previously created.
                fiWaterMeters = new FileInfo(strWaterMeters)

                rem Find out whether a list of water meters was previously created 
                rem and was stored in the string file declared above.
                if fiWaterMeters.Exists)
                
                    rem If that file exists already, create a Stream object 
rem for it with a read-only status.
                    using (fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open,
                                                          FileAccess.Read, FileShare.Read))
                        rem Pass the list of water meters to the XML Dom object created earlier
                        xdWaterMeters.Load(fsWaterMeters)
                    end using
                else
                
                    rem If a file for water meters was not previously created, create it now...
                    using (fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Create,
                                                          FileAccess.Write, FileShare.Write))
                    
                        rem and create the root XML element for it
                        xdWaterMeters.LoadXml("<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
                                              "<water-meters></water-meters>")
                        rem Make sure you save the new file
                        xdWaterMeters.Save(fsWaterMeters)
                    end using
                end if

                rem Now that the file exists, open it
                using (fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.OpenOrCreate,
                                                      FileAccess.ReadWrite, FileShare.ReadWrite))
                
                    rem Start creating a new Water Meter XML element
                    XmlElement xeWaterMeter = xdWaterMeters.CreateElement("water-meter")

                    rem Use the values that the user had typed in the Create form.
rem Use those values to create the child elements of the new water meter node.
rem Assign the combination of child elements to the new water meter node.
                    xeWaterMeter.InnerXml = "<meter-number>" + wm.MtbMeterNumber.Text + "</meter-number>" +
                                            "<make>" + wm.TxtMake.Text + "</make>" +
                                            "<model>" + wm.TxtModel.Text + "</model>" +
                                            "<meter-size>" + wm.TxtMeterSize.Text + "</meter-size>"
                    rem Once the XML element is ready, add/append it to the XML Dom that was previously created.
                    xdWaterMeters.DocumentElement!.AppendChild(xeWaterMeter)
                    rem Once the new element has been created and add it to the file, save that file
                    xdWaterMeters.Save(fsWaterMeters)
                end using
            end if

            rem Whenever the user has finished using the Create form, 
            rem make an attempt to display the list of water meters.
            ShowWaterMeters()
        end sub

        private sub BtnViewWaterMeter_Click(sender As Object, e As EventArgs)
        
            rem Get a reference to the dialog box that is used 
            rem to view information about a water meter.
            Details view = new()
            rem Display that dialog box
            view.ShowDialog()

            rem After using the dialog box, make an attempt to display the list of water meters.
            ShowWaterMeters()
        end sub

        private sub BtnEditWaterMeter_Click(sender As Object, e As EventArgs)
        
            rem Get a reference to the dialog box that is used 
            rem to update the details of a water meter.
            Editor editor = new()
            rem Display that dialog box
            editor.ShowDialog()

            rem After using the dialog box, make an attempt to display the list of water meters.
            ShowWaterMeters()
        end sub

        private sub BtnDeleteWateMeter_Click(sender As Object, e As EventArgs)
            Delete del = new Delete()
            del.ShowDialog()

            ShowWaterMeters()
        end sub

        private sub BtnClose_Click(sender As Object, e As EventArgs)
            Close()
        end sub
    }
}

To execute the application, on the main menu, click Debug -> Start Without Debugging:
On the Central form, click the Water Meters button:
On the Central form of the water meters, click the Delete Water Meter button:
In the Meter # text, type 588-279-663
Click the Find button:
Click the Delete button:
Read the text on the message box:
On the message box, click Yes
Close the forms and return to your programming environment
From the Windows Explorer, open the WaterMeters.xml file
Replace the content of the file with the provided file
Save the file
Return to your programming environment

Customers

Introduction

Customers are the entities that use the services of the bussiness whose application we are building. In this seciton, we will createthe forms that can assist a user with customers-based operations.

Customers Accounts

Our application will use a database that contains a list of customers. As seen with water meter records, some time to time, a user will want to view the customers records. To display a list of customers, we will create a form equipped with a list view.

Practical Learning: Displaying Customers Accounts

To create a folder, in the Solution Explorer, right-click the StellarWaterPoint1 project -> Add -> New Folder
Type Customers as the name of the folder
To create a form, in the Solution Explorer, right-click Customers -> Add -> Form (Windows Forms)...
Type Central
Click Add
In the Toolbox, click the ListView button and click the form

In the Properties window, change the characteristics of the list view as follows:

Control		(Name)	Other Properties
ListView		LvwCustomers	FullRowSelect: True GridLines: True View: Details Anchor: Top, Bottom, Left, Right

On the form, right-click the list view and click Edit Columns...

Create the columns as follows:

(Name)	Text	TextAlign	Width
colCustomerId	Id		40
colAccountNumber	Account #	Center	150
colAccountName	Account Name		200
colMeterNumber	Meter #	Center	100
colAccountType	Account Type		200
colAddress	Address		250
colCity	City		125
colCounty	County		125
colState	State	Center
colZIPCode	ZIP-Code	Center	125

Click OK
Doubte-click an unoccupied area of the form to generate its Load event

Change the document as follows:

import System.Xml

namespace StellarWaterPoint1.Customers

    public partial class Central : Form
    
        public Central()
        {
            InitializeComponent()
        }

        private sub ShowCustomers()
        {
            int i = 1;

            lvwCustomers.Items.Clear()

            XmlDocument xdCustomers = new XmlDocument()
            string? strCustomers = "C:\Stellar Water Point1\Customers.xml"

            FileInfo? fiCustomers = new FileInfo(strCustomers)

            if fiCustomers.Exists)
            {
                using  fsCustomers as FileStream= new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdCustomers.Load(fsCustomers)
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.ChildNodes;

                    for each xnCustomer as XmlNode  in xnlCustomers
                    {
                        dim lviCustomer as ListViewItem = new ListViewItem(i.ToString())

                        lviCustomer.SubItems.Add(xnCustomer.FirstChild!.InnerText)   rem Account #
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling!.InnerText)   rem Account Name
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling!.InnerText) rem Meter #
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling!.InnerText)   rem Account Type
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText)   rem Address
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.InnerText)   rem City
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText)   rem County
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText)   rem State
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText) rem ZIP-Code

                        lvwCustomers.Items.Add(lviCustomer)

                        i++;
                    }
                }
            }
        }

        private sub Central_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        {
            ShowCustomers()
        }       
    }
}

In the Solution Explorer, double-click WaterDistribution.cs to diaply the primary form of the application
From the Toolbox, add a button to the form

From the Properties window, change the characteristics of the button as follows:

Control		(Name)	Text	Font
Button		BtnCustomers	&Customers...	Times New Roman, 24pt, style=Bold

On the form, double-click the Customers button

Implement the event as follows:

namespace StellarWaterPoint1
{
    public partial class WaterDistribution : Form
    {
        public WaterDistribution()
        {
            InitializeComponent()
        }

        private sub WaterDistribution_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        {
            rem If the directory for the database doesn't yet exist, create it
            Directory.CreateDirectory("C:\Stellar Water Point")
        }

        private sub BtnCustomers_Click(sender As Object, e As EventArgs)
        {
            Customers.Central central = new Customers.Central()

            central.ShowDialog()
        }

        private sub BtnWaterMeters_Click(sender As Object, e As EventArgs)
        {
            WaterMeters.Central central = new WaterMeters.Central()

            central.ShowDialog()
        }
    }
}

A Customer's Account

As mentioned already, our application will use a database that contains a list of customers. This means that a customer must have an account. We will create a form to let the user create an account. Each customer account must have an associated water meter.

Practical Learning: Creating a Customer Account

In the Solution Explorer, right-click the Customers folder -> Add -> Form (Windows Forms)...
Type Create as the name of the file
Click Add

Design the form as follows:

Stellar Water Point - New Customer Account

Control	(Name)	Text	Other Properties
Label		&Account #:
MaskedTextBox	MtbAccountNumber		Masked: 0000-000-0000
Label		&Account Name:
TextBox	TxtAccountName
Label		&Meter #:
MaskedTextBox	MtbMeterNumber		Masked: 000-000-000
Button	BtnFindWaterMeter	&Find Water Meter
Label		Meter &Details:
TextBox	TxtMeterDetails		Enabled: False
Label		&Account Type:
ComboBox	cbxAccountsTypes		Items: OTH - Other BUS - General Business RES - Residential Household SGO - Social/Government/Non - Profit Organization UUO - Unidentified or Unclassified Type of Organization WAT - Water Intensive Business(Laudromat, Hair Salon, Restaurant, etc
Label		&Address:
TextBox	TxtAddress
Label		C&ity:
TextBox	TxtCity
Label		C&ounty:
TextBox	TxtCounty
Label		&State:
TextBox	TxtState
Label		&ZIP-Code:
MaskedTextBox	MtbZIPCode		Masked: Zip-Code
Button	BtnSaveCustomerAccount	S&ave Customer Account	DialogResult: OK
Button	BtnClose	&Close	DialogResult: Cancel

Using the Properties window, change some characteristics of the form as follows:

FormBorderStyle: FixedDialog
Text:            Stellar Water Point - Customer Account Setup
StartPosition:   CenterScreen
AcceptButton:    BtnSaveCustomerAccount
CancelButton:    BtnClose
MinimizeBox:     False
MaximizeBox:     False

On the form, double-click the Find Water Meter button

Change the document as follows:

import System.Xml

namespace StellarWaterPoint1.Customers
{
    public partial class Create : Form
    {
        public Create()
        {
            InitializeComponent()
        }

        private sub BtnFindWaterMeter_Click(sender As Object, e As EventArgs)
        {
            rem Create an XML Dom object
            dim xdWaterMeters as XmlDocument = new XmlDocument()
            rem Declare a string variable and assign the file of water meters to it
            dim strWaterMeters as string= "C:\Stellar Water Point1\WaterMeters.xml"
            rem Create a FileInfo object to manage the file that has the water meters
            dim fiWaterMeters as FileInfo= new FileInfo(strWaterMeters)

            rem Find out whether a file for water meters exists already
            if fiWaterMeters.Exists)
            {
                rem If a file for water meters exists already, create a Stream object for it
                using  fsWaterMeters as FileStream= new FileStream(fiWaterMeters.FullName, FileMode.Open,
                                                                  FileAccess.Read, FileShare.Read))
                {
                    rem From the file of water meters, store the list of water meters 
rem in the XML Dom that was previously created.
                    xdWaterMeters.Load(fsWaterMeters)

                    rem Check the list of water meters. 
rem Find a water meter that has the same name as the meter number that the user typed.
                    dim xnlWaterMeters  as XmlNodeList = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + MtbMeterNumber.Text + "']")!;

                    rem If such a water meter exists...
                    for each xnWaterMeter  as XmlNode in xnlWaterMeters)
                    {
                        rem ... store its details in the meter details text box.
                        TxtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")"
                    }
                }
            }
        }
    }
}

In the Solution Explorer, below the Customers folder, double-click Central.cs
From the Toolbox, add a button to the form below the list view

Change the characteristics of the button as follows:

Control	(Name)	Other Properties
ListView	LvwCustomers
Button	BtnCreateCustomerAccount	&Create Customer Account... Anchor: Bottom, Right

Double-click the Create Customer Account button

Change the document as follows:

import System.Xml

namespace StellarWaterPoint1.Customers
{
    public partial class Central : Form
    {
        public Central()
        {
            InitializeComponent()
        }

        private sub ShowCustomers()
        {
            int i = 1;

            lvwCustomers.Items.Clear()

            XmlDocument xdCustomers = new XmlDocument()
            string? strCustomers = "C:\Stellar Water Point1\Customers.xml"

            FileInfo? fiCustomers = new FileInfo(strCustomers)

            if fiCustomers.Exists)
            {
                using  fsCustomers as FileStream= new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdCustomers.Load(fsCustomers)
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.ChildNodes;

                    for each xnCustomer as XmlNode  in xnlCustomers
                    {
                        dim lviCustomer as ListViewItem = new ListViewItem(i.ToString())

                        lviCustomer.SubItems.Add(xnCustomer.FirstChild!.InnerText)   rem Account #
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling!.InnerText)   rem Account Name
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling!.InnerText) rem Meter #
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling!.InnerText)   rem Account Type
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText)   rem Address
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.InnerText)   rem City
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText)   rem County
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText)   rem State
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText) rem ZIP-Code

                        lvwCustomers.Items.Add(lviCustomer)

                        i++;
                    }
                }
            }
        }

        private sub Central_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        {
            rem When the form opens, try displaying the list of customers
            ShowCustomers()
        }

        private sub BtnCreateCustomerAccount_Click(sender As Object, e As EventArgs)
        {
            Create create = new Create()

            if create.ShowDialog() =MsgBoxResult.OK)
            {
                rem Make sure the user provides an account number for the new account. 
                rem If not, don't create the account.
                if string.IsNullOrEmpty(create.MtbAccountNumber.Text))
                {
                    MsgBox("You must provide an account number for the new customer. " +
                                    "Otherwise, the account cannot be created.",
                                    MsgBoxStyle.OkOnly Or MsgBoxStyle.Information,
                                    "Stellar Water Point")

                    Exit Sub
                }

                rem If the meter details text box is empty, it means the user didn't enter
                rem a meter number, in which case there is no water meter associated 
                rem with the account. The account cannot be created.
                if string.IsNullOrEmpty(create.TxtMeterDetails.Text))
                {
                    MsgBox("You must enter a water meter to associate with a new customer's account.",
                                    MsgBoxStyle.OkOnly Or MsgBoxStyle.Information,
                                    "Stellar Water Point")
                    
                    Exit Sub
                }
                
                rem Create a FileInfo object that will be used to manage a file
                FileInfo? fiCustomers = nothing
                rem Start a Stream object that will be used to manage a file
                FileStream? fsCustomers = nothing
                rem Create an XML Dom
                XmlDocument xdCustomers = new XmlDocument()
                rem Declare a string variable for the file that contains a list of customers
                string? strCustomers = "C:\Stellar Water Point1\Customers.xml"
                
                rem Pass the file of customers to the FileInfo object that was started
                fiCustomers = new FileInfo(strCustomers)

                rem Find out whether that file was already created
                if fiCustomers.Exists)
                {
                    rem If that file was already created, open it through 
rem the Stream object that was previously initiated.
                    using (fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open,
                                                        FileAccess.Read, FileShare.Read))
                    {
                        rem Pass the Stream object to the XML Dom that was previously created.
                        xdCustomers.Load(fsCustomers)
                    }
                }
                else
                {
                    rem If the file of customers was not created already, start by 
rem initializing the Stream object that was previously initiated.
                    using (fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Create, FileAccess.Write, FileShare.Write))
                    {
                        rem Create a root to start the XML file
                        xdCustomers.LoadXml("<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
                                            "<customers></customers>")
                        rem Once the file has been started, save it
                        xdCustomers.Save(fsCustomers)
                    }
                }

                rem Now that we have an XML file for customers, open it
                using (fsCustomers = new FileStream(fiCustomers.FullName, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.ReadWrite))
                {
                    rem We want to create an XML element to be added to the XML file.
rem To start, create an XML element named "customer".
                    XmlElement xeCustomer = xdCustomers.CreateElement("customer")

                    rem Create/Format the child nodes of the "customer" element
                    xeCustomer.InnerXml = "<account-number>" + create.MtbAccountNumber.Text + "</account-number>" +
                                          "<account-name>"   + create.TxtAccountName.Text   + "</account-name>"   +
                                          "<meter-number>"   + create.MtbMeterNumber.Text   + "</meter-number>"   +
                                          "<account-type>"   + create.cbxAccountsTypes.Text + "</account-type>"   +
                                          "<address>"        + create.TxtAddress.Text       + "</address>"        +
                                          "<city>"           + create.TxtCity.Text          + "</city>"           +
                                          "<county>"         + create.TxtCounty.Text        + "</county>"         +
                                          "<state>"          + create.TxtState.Text         + "</state>"          +
                                          "<zip-code>"       + create.MtbZIPCode.Text       + "</zip-code>"
                    xdCustomers.DocumentElement!.AppendChild(xeCustomer)
                    xdCustomers.Save(fsCustomers)
                }
            }

            ShowCustomers()
        }
    }
}

To execute the application, on the main menu, click Debug -> Start Without Debugging:
On the Water Distribution form, click the Customers button:
On the Central form of the customers, click the Create Customer Account button:
In the account # text box, type 9279-570-8394
In the meter # text box, type 799-528-461
Click the Find water meter button

Enter the other values as follows:

Account #:    9279-570-8394
Account Name: Thomas Stones
Meter #:      799-528-461
Account Type: RES - Residential Household
Address:      10252 Broward Ave #D4
City:         Frederick
County:       Frederick
State:        MD
ZIP-Code:     21703-4422

Click Save Customer Account

In the same way, create the following two records:

Account #	Account Name	Meter #	Account Type	Address	City	County	State	ZIP-Code
4086-938-4783	Hernola Dough	594-827-359	UUO - Unidentified or Unclassified Type of Organization	10 10 Hexagonal Drv	Winston	Yoke	Penn	11402-4411
7080-583-5947	Sunny Yard	827-508-248	WAT - Water Intensive Business(Laudromat, Hair Salon, Restaurant, etc	663 Sherry Wood East Street	Shimpstown	Franklin	PA	17236-2626

Close the forms and return to your programming environment

A Review of a Customer's Account

Some time to time, a user will want to review the details of a customer's account. We will create a form to assist the user with this.

Practical Learning: Creating a Water Meter Record

To create a form, in the Solution Explorer, right-click Customers -> Add -> Form (Windows Forms)...
For the Name of the form, type Details
Press Enter

Design the form as follows:

Stellar Water Point - New Customer Account

Control	(Name)	Text	Other Properties
Label		&Account #:
MaskedTextBox	MtbAccountNumber		Masked: 0000-000-0000
Button	BtnFindCustomerAccount	&Find Customer Account
Label		Account Name:
TextBox	TxtAccountName		Enabled: False
Label		Meter #:
TextBox	TxtMeterNumber		Enabled: False
Label		Meter Details:
TextBox	TxtMeterDetails		Enabled: False
Label		Account Type:
TextBox	TxtAccountType		Enabled: False
Label		Address:
TextBox	TxtAddress		Enabled: False
Label		City:
TextBox	TxtCity		Enabled: False
Label		County:
TextBox	TxtCounty		Enabled: False
Label		State:
TextBox	TxtState		Enabled: False
Label		ZIP-Code:	Enabled: False
TextBox	TxtZIPCode		Enabled: False
Button	BtnClose	&Close

Using the Properties window, change some characteristics of the form as follows:

FormBorderStyle: FixedDialog
Text:            Stellar Water Point - Customer Account Setup
StartPosition:   CenterScreen
MinimizeBox:     False
MaximizeBox:     False

On the form, double-click the Find Cust&omer Account button

Implement the event as follows:

import System.Xml

namespace StellarWaterPoint1.Customers
{
    public partial class Details : Form
    {
        public Details()
        {
            InitializeComponent()
        }

        private sub BtnFindCustomerAccount_Click(sender As Object, e As EventArgs)
        {
            XmlDocument xdCustomers = new XmlDocument()
            string? strCustomers = "C:\Stellar Water Point1\Customers.xml"

            FileInfo? fiCustomers = new FileInfo(strCustomers)

            string strMeterNumber = string.Empty;

            if fiCustomers.Exists)
            {
                using  fsCustomers as FileStream= new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdCustomers.Load(fsCustomers)
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + MtbAccountNumber.Text + "']")!;

                    for each xnCustomer as XmlNode  in xnlCustomers
                    {
                        //MtbAccountNumber.Text = xnCustomer.NextSibling.InnerText   rem Meter #
                        TxtAccountName.Text   = xnCustomer.NextSibling.InnerText rem Account Name
                        TxtMeterNumber.Text   = xnCustomer.NextSibling.NextSibling.InnerText   rem Meter Number
                        strMeterNumber        = xnCustomer.NextSibling.NextSibling.InnerText   rem Meter Number
                        TxtAccountType.Text   = xnCustomer.NextSibling.NextSibling.NextSibling.InnerText   rem Account Type
                        TxtAddress.Text       = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.InnerText   rem Address
                        TxtCity.Text          = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.InnerText   rem City
                        TxtCounty.Text        = xnCustomer.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling.InnerText   rem County
                        TxtState.Text         = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText   rem State
                        TxtZIPCode.Text       = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText rem ZIP-Code
                    }
                }
            }

            dim xdWaterMeters as XmlDocument = new XmlDocument()
            dim strWaterMeters as string= "C:\Stellar Water Point10\WaterMeters.xml"

            dim fiWaterMeters as FileInfo= new FileInfo(strWaterMeters)

            if fiWaterMeters.Exists)
            {
                using  fsWaterMeters as FileStream= new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterMeters.Load(fsWaterMeters)
                    dim xnlWaterMeters  as XmlNodeList = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;

                    for each xnWaterMeter  as XmlNode in xnlWaterMeters)
                    {
                        TxtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")"
                    }
                }
            }
        }
    }
}

Return to the form and double-click the Close button

Implement the event as follows:

import System.Xml

namespace StellarWaterPoint1.Customers
{
    public partial class Details : Form
    {
        public Details()
        {
            InitializeComponent()
        }

        private sub BtnFindCustomerAccount_Click(sender As Object, e As EventArgs)
        {
            rem Create an XML DOM object for the customers records
            XmlDocument xdCustomers = new XmlDocument()
            rem Declare a variable for a file that holds the list of customers
            string? strCustomers = "C:\Stellar Water Point10\Customers.xml"

            rem Create a FileInfo object for the customers
            FileInfo? fiCustomers = new FileInfo(strCustomers)

            rem We will need to know the water meter associated with this customer account
            string strMeterNumber = string.Empty;

            rem Check whether the file that holds a list of customers exists
            if fiCustomers.Exists)
            {
                rem If that exists, open it and pass it to a FileStream object
                using  fsCustomers as FileStream= new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    rem Get the list of customers and pass the records to the XML DOM object created earlier
                    xdCustomers.Load(fsCustomers)
                    rem Create an XmlNodeList list of customers using XPath
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + MtbAccountNumber.Text + "']")!;

                    rem Check each node of the XML record and display its values in each Windows control on the form
                    for each xnCustomer as XmlNode  in xnlCustomers
                    {
                        //MtbAccountNumber.Text = xnCustomer.NextSibling.InnerText   rem Meter #
                        TxtAccountName.Text = xnCustomer.NextSibling.InnerText rem Account Name
                        TxtMeterNumber.Text = xnCustomer.NextSibling.NextSibling.InnerText   rem Meter Number
                        strMeterNumber = xnCustomer.NextSibling.NextSibling.InnerText   rem Meter Number
                        TxtAccountType.Text = xnCustomer.NextSibling.NextSibling.NextSibling.InnerText   rem Account Type
                        TxtAddress.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.InnerText   rem Address
                        TxtCity.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.InnerText   rem City
                        TxtCounty.Text = xnCustomer.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling.InnerText   rem County
                        TxtState.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText   rem State
                        TxtZIPCode.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText rem ZIP-Code
                    }
                }
            }

            rem Create an XML DOM object for the water meters records
            dim xdWaterMeters as XmlDocument = new XmlDocument()
            rem Declare a variable for a file that holds the list of water meters
            dim strWaterMeters as string= "C:\Stellar Water Point10\WaterMeters.xml"

            rem Create a FileInfo object for the customers
            dim fiWaterMeters as FileInfo= new FileInfo(strWaterMeters)

            rem Check whether the file that holds a list of water meters exists
            if fiWaterMeters.Exists)
            {
                rem Get the list of water meters and pass the records to the XML DOM object
                using  fsWaterMeters as FileStream= new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    rem Get the list of water meters and pass the records to the XML DOM object
                    xdWaterMeters.Load(fsWaterMeters)
                    rem Create an XmlNodeList list of water meters using XPath
                    dim xnlWaterMeters  as XmlNodeList = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;

                    rem Check each node of the XML record
                    for each xnWaterMeter  as XmlNode in xnlWaterMeters)
                    {
                        rem Get the values for the water meter.
    rem Create a sentence and display it in the Meter Details text box.
                        TxtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")"
                    }
                }
            }
        }

        private sub BtnClose_Click(sender As Object, e As EventArgs)
        {
            Close()
        }
    }
}

In the Solution Explorer, below the Customers folder, double-click Central.cs to open its form
From the Toolbox, add a button to the form below the list view and to the right of the Create Customer Account button

Change the characteristics of the button as follows:

Control		(Name)	Other Properties
Button		BtnViewCustomerAccount	&View Customer Account... Anchor: Bottom, Right

Double-click the View Customer Account button

Change the document as follows:

import System.Xml

namespace StellarWaterPoint1.Customers
{
    public partial class Details : Form
    {
        public Details()
        {
            InitializeComponent()
        }

        private sub BtnFindCustomerAccount_Click(sender As Object, e As EventArgs)
        {
            XmlDocument xdCustomers = new XmlDocument()
            string? strCustomers = "C:\Stellar Water Point10\Customers.xml"

            FileInfo? fiCustomers = new FileInfo(strCustomers)

            string strMeterNumber = string.Empty;

            if fiCustomers.Exists)
            {
                using  fsCustomers as FileStream= new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdCustomers.Load(fsCustomers)
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + MtbAccountNumber.Text + "']")!;

                    for each xnCustomer as XmlNode  in xnlCustomers
                    {
                        //MtbAccountNumber.Text = xnCustomer.NextSibling.InnerText rem Meter #
                        TxtAccountName.Text     = xnCustomer.NextSibling.InnerText rem Account Name
                        TxtMeterNumber.Text     = xnCustomer.NextSibling.NextSibling.InnerText   rem Meter Number
                        strMeterNumber          = xnCustomer.NextSibling.NextSibling.InnerText   rem Meter Number
                        TxtAccountType.Text     = xnCustomer.NextSibling.NextSibling.NextSibling.InnerText   rem Account Type
                        TxtAddress.Text         = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.InnerText   rem Address
                        TxtCity.Text            = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.InnerText   rem City
                        TxtCounty.Text          = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling.InnerText   rem County
                        TxtState.Text           = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText   rem State
                        TxtZIPCode.Text         = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText rem ZIP-Code
                    }
                }
            }

            dim xdWaterMeters as XmlDocument = new XmlDocument()
            dim strWaterMeters as string= "C:\Stellar Water Point10\WaterMeters.xml"

            dim fiWaterMeters as FileInfo= new FileInfo(strWaterMeters)

            if fiWaterMeters.Exists)
            {
                using  fsWaterMeters as FileStream= new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterMeters.Load(fsWaterMeters)
                    dim xnlWaterMeters  as XmlNodeList = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;

                    for each xnWaterMeter  as XmlNode in xnlWaterMeters)
                    {
                        TxtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")"
                    }
                }
            }
        }
    }
}

To execute the application, on the main menu, click Debug -> Start Without Debugging
On the Water Distribution form, click the Customers button:
On the Central form of customers, click the View Customer Account button:
In the Account # text box, type 4086-938-4783
Click the Find Customer Account button:
Close the Details form
Close the forms and return to your programming environment

Updating a Customer's Account

Some time to time, a piece of information changes about a customer's account. When that happens, a user must update such an account. To assist the users in performing such an operation, we will create a form.

Practical Learning: Updating a Water Meter

To create a form, in the Solution Explorer, right-click WaterMeters -> Add -> Form (Windows Forms)...
For the Name of the file, type Editor as the name of the form
Click Add
Resize the Editor form to have the same size as the Create form of the Customers section
Copy everything from the Create form of the Customers section and paste it in the Editor form of the Customers section

Change the design of the form as follows:

Stellar Water Point - New Customer Account

Control	(Name)	Text	Other Properties
Button	BtnFindCustomerAccount	&Find Customer Account
Button	BtnUpdateWateMeter	&Update Water Meter	DialogResult: OK
Button	BtnClose	&Close	DialogResult: Cancel

Using the Properties window, change some characteristics of the form as follows:

FormBorderStyle: FixedDialog
Text:            Stellar Water Point - Customer Account Editor
StartPosition:   CenterScreen
AcceptButton:    BtnUpdateWateMeter
CancelButton:    BtnClose
MinimizeBox:     False
MaximizeBox:     False

On the form, double-click the Find Customer Account button

Change the document as follows:

import System.Xml

namespace StellarWaterPoint1.Customers
{
    public partial class Editor : Form
    {
        public Editor()
        {
            InitializeComponent()
        }

        private sub BtnFindCustomerAccount_Click(sender As Object, e As EventArgs)
        {
            XmlDocument xdCustomers = new XmlDocument()
            string? strCustomers = "C:\Stellar Water Point10\Customers.xml"

            FileInfo? fiCustomers = new FileInfo(strCustomers)

            string strMeterNumber = string.Empty;

            if fiCustomers.Exists)
            {
                using  fsCustomers as FileStream= new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdCustomers.Load(fsCustomers)
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + MtbAccountNumber.Text + "']")!;

                    for each xnCustomer as XmlNode  in xnlCustomers
                    {
                        //MtbAccountNumber.Text = xnCustomer.NextSibling.InnerText   rem Meter #
                        TxtAccountName.Text   = xnCustomer.NextSibling.InnerText rem Account Name
                        MtbMeterNumber.Text   = xnCustomer.NextSibling.NextSibling.InnerText   rem Meter Number
                        strMeterNumber        = xnCustomer.NextSibling.NextSibling.InnerText   rem Meter Number
                        cbxAccountsTypes.Text = xnCustomer.NextSibling.NextSibling.NextSibling.InnerText   rem Account Type
                        TxtAddress.Text       = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.InnerText   rem Address
                        TxtCity.Text          = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.InnerText   rem City
                        TxtCounty.Text        = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling.InnerText   rem County
                        TxtState.Text         = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText   rem State
                        MtbZIPCode.Text       = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText rem ZIP-Code
                    }
                }
            }

            dim xdWaterMeters as XmlDocument = new XmlDocument()
            dim strWaterMeters as string= "C:\Stellar Water Point10\WaterMeters.xml"

            dim fiWaterMeters as FileInfo= new FileInfo(strWaterMeters)

            if fiWaterMeters.Exists)
            {
                using  fsWaterMeters as FileStream= new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterMeters.Load(fsWaterMeters)
                    dim xnlWaterMeters  as XmlNodeList = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;

                    for each xnWaterMeter  as XmlNode in xnlWaterMeters)
                    {
                        TxtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")"
                    }
                }
            }
        }
    }
}

Return to the form and double-click the Find Water Meter button

Implement the event as follows:

import System.Xml

namespace StellarWaterPoint1.Customers
{
    public partial class Editor : Form
    {
        public Editor()
        {
            InitializeComponent()
        }

        private sub BtnFindCustomerAccount_Click(sender As Object, e As EventArgs)
        {
            XmlDocument xdCustomers = new XmlDocument()
            string? strCustomers = "C:\Stellar Water Point10\Customers.xml"

            FileInfo? fiCustomers = new FileInfo(strCustomers)

            string strMeterNumber = string.Empty;

            if fiCustomers.Exists)
            {
                using  fsCustomers as FileStream= new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdCustomers.Load(fsCustomers)
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + MtbAccountNumber.Text + "']")!;

                    for each xnCustomer as XmlNode  in xnlCustomers
                        rem MtbAccountNumber.Text = xnCustomer.NextSibling.InnerText
                        TxtAccountName.Text   = xnCustomer.NextSibling.InnerText
                        MtbMeterNumber.Text   = xnCustomer.NextSibling.NextSibling.InnerText
                        strMeterNumber        = xnCustomer.NextSibling.NextSibling.InnerText
                        cbxAccountsTypes.Text = xnCustomer.NextSibling.NextSibling.NextSibling.InnerText
                        TxtAddress.Text       = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.InnerText
                        TxtCity.Text          = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.InnerText
                        TxtCounty.Text        = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtState.Text         = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        MtbZIPCode.Text       = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                    next
                }
            }

            dim xdWaterMeters as XmlDocument = new XmlDocument()
            dim strWaterMeters as string= "C:\Stellar Water Point10\WaterMeters.xml"

            dim fiWaterMeters as FileInfo= new FileInfo(strWaterMeters)

            if fiWaterMeters.Exists)
            {
                using  fsWaterMeters as FileStream= new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterMeters.Load(fsWaterMeters)
                    dim xnlWaterMeters  as XmlNodeList = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;

                    for each xnWaterMeter  as XmlNode in xnlWaterMeters)
                    {
                        TxtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")"
                    }
                }
            }
        }

        private sub BtnFindWateMeter_Click(sender As Object, e As EventArgs)
        {
            dim xdWaterMeters as XmlDocument = new XmlDocument()
            dim strWaterMeters as string= "C:\Stellar Water Point10\WaterMeters.xml"
            dim fiWaterMeters as FileInfo= new FileInfo(strWaterMeters)

            if fiWaterMeters.Exists)
            {
                using  fsWaterMeters as FileStream= new FileStream(fiWaterMeters.FullName, FileMode.Open,
                                                                  FileAccess.Read, FileShare.Read))
                {
                    xdWaterMeters.Load(fsWaterMeters)

                    dim xnlWaterMeters  as XmlNodeList = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + MtbMeterNumber.Text + "']")!;

                    for each xnWaterMeter  as XmlNode in xnlWaterMeters)
                    {
                        TxtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")"
                    }
                }
            }
        }
    }
}

In the Solution Explorer, below the Customers folder, double-click Central.cs
From the Toolbox, add a button to the form below the list view and on the right side of the View Customer Account button

Change the characteristics of the button as follows:

Control	(Name)	Text	Other Properties
ListView	LvwCustomers		No Change
Button	BtnNewCustomerAccount		No Change
Button	BtnViewCustomerAccount		No Change
Button	BtnEditCustomerAccount	&Edit Water Meter...	Anchor: Bottom, Right

Display the Central form of the Customers folder
Double-click the Update Water Meter button

Implement the event as follows:

import System.Xml

namespace StellarWaterPoint1.Customers
{
    public partial class Central : Form
    {
        public Central()
        {
            InitializeComponent()
        }

        private sub ShowCustomers()
        {
            . . .
        }

        private sub Central_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        {
            ShowCustomers()
        }

        private sub BtnCreateCustomerAccount_Click(sender As Object, e As EventArgs)
        {
            . . .
        }

        private sub ViewCustomerAccount_Click(sender As Object, e As EventArgs)
        {
            Details det = new Details()

            det.ShowDialog()
        }

        private sub BtnEditCustomerAccount_Click(sender As Object, e As EventArgs)
        {
            Editor editor = new()
            XmlDocument xdCustomers = new XmlDocument()
            string? strCustomers = "C:\Stellar Water Point10\Customers.xml"

            if editor.ShowDialog() =MsgBoxResult.OK
                xdCustomers.Load(strCustomers)

                XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.GetElementsByTagName("account-number")

                for each xnCustomer as XmlNode  in xnlCustomers
                    if xnCustomer.InnerText.Contains(editor.MtbAccountNumber.Text)
                        xnCustomer.ParentNode!.InnerXml = "<account-number>" + editor.MtbAccountNumber.Text + "</account-number>" +
                                              "<account-name>" + editor.TxtAccountName.Text + "</account-name>" +
                                              "<meter-number>" + editor.MtbMeterNumber.Text + "</meter-number>" +
                                              "<account-type>" + editor.cbxAccountsTypes.Text + "</account-type>" +
                                              "<address>" + editor.TxtAddress.Text + "</address>" +
                                              "<city>" + editor.TxtCity.Text + "</city>" +
                                              "<county>" + editor.TxtCounty.Text + "</county>" +
                                              "<state>" + editor.TxtState.Text + "</state>" +
                                              "<zip-code>" + editor.MtbZIPCode.Text + "</zip-code>"

                        xdCustomers.Save(strCustomers)
                        Exit For
                    end if
                next
            end if

            ShowCustomers()    
        }
    }
}

To execute the application, on the main menu, click Debug -> Start Without Debugging
On the main form of the application, click the Customers button:
Click the Edit Customer Account button:
In the Account # text, type 4086-938-4783
Click the Find Customer Account button

Change the values as follows:

Account Name: Bernotte's Doughnuts
Meter #:      580-742-825 and click Find Water Meter
Account Type: BUS	- General Business
Address:      10103 Hexagon Drive
City:         Winterstown
County:       York
State:        PA
ZIP-Code:     17402-8828

Stellar Water Point - New Water Meter

Click the Update Customer Account button:
Close the forms and return to your programming environment

Deleting a Customer's Account

If a customer's account is not necessary anymore, the user can remove that account. To assist the user with this operation, we will create a form with necessary buttons.

Practical Learning: Deleting a Customer Account

To create a form, in the Solution Explorer, right-click WaterMeters -> Add -> Form(Windows Forms)...
In the Name text box, replace the string with Delete as the name of the form
Press Enter
Resize the Delete form to have the same size as the Details form
Copy everything from the Details form and paste it in the Delete form

Change the bottom button as follows:

Stellar Water Point - New Water Meter

Control	(Name)	Text	Othe Properties
Button	BtnDeleteCustomerAccount	&Delete Water Meter	DialogResult: OK
Button	BtnClose	&Close	DialogResult: Cancel

Using the Properties window, change some characteristics of the form as follows:

FormBorderStyle: FixedDialog
Text:            Stellar Water Point - Customer Account Deletion
StartPosition:   CenterScreen
AcceptButton:    BtnDeleteCustomerAccount
CancelButton:    BtnClose
MinimizeBox:     False
MaximizeBox:     False

On the form, double-click the Find Customer Account button

Change the document as tollows:

import System.Xml

namespace StellarWaterPoint1.Customers
{
    public partial class Delete : Form
    {
        public Delete()
        {
            InitializeComponent()
        }

        private sub BtnFindCustomerAccount_Click(sender As Object, e As EventArgs)
        {
            rem Create an XML DOM object for the customers records
            XmlDocument xdCustomers = new XmlDocument()
            rem Declare a variable for a file that holds the list of customers
            string? strCustomers = "C:\Stellar Water Point10\Customers.xml"

            rem Create a FileInfo object for the customers
            FileInfo? fiCustomers = new FileInfo(strCustomers)

            rem We will need to know the water meter associated with this customer account
            string strMeterNumber = string.Empty;

            rem Check whether the file that holds a list of customers exists
            if fiCustomers.Exists
                rem If that exists, open it and pass it to a FileStream object
                using  fsCustomers as FileStream= new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read)
                    rem Get the list of customers and pass the records to the XML DOM object created earlier
                    xdCustomers.Load(fsCustomers)
                    rem Create an XmlNodeList list of customers using XPath
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + MtbAccountNumber.Text + "']")!;

                    rem Check each node of the XML record and display its values in each Windows control on the form
                    for each xnCustomer as XmlNode  in xnlCustomers
                        rem MtbAccountNumber.Text = xnCustomer.NextSibling.InnerText
                        TxtAccountName.Text = xnCustomer.NextSibling.InnerText
                        TxtMeterNumber.Text = xnCustomer.NextSibling.NextSibling.InnerText
                        strMeterNumber = xnCustomer.NextSibling.NextSibling.InnerText
                        TxtAccountType.Text = xnCustomer.NextSibling.NextSibling.NextSibling.InnerText
                        TxtAddress.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.InnerText
                        TxtCity.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.InnerText
                        TxtCounty.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtState.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtZIPCode.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                    next
                end using
            end if

            rem Create an XML DOM object for the water meters records
            dim xdWaterMeters as XmlDocument = new XmlDocument()
            rem Declare a variable for a file that holds the list of water meters
            dim strWaterMeters as string= "C:\Stellar Water Point10\WaterMeters.xml"

            rem Create a FileInfo object for the customers
            dim fiWaterMeters as FileInfo= new FileInfo(strWaterMeters)

            rem Check whether the file that holds a list of water meters exists
            if fiWaterMeters.Exists
                rem Get the list of water meters and pass the records to the XML DOM object
                using  fsWaterMeters as FileStream= new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read)
                    rem Get the list of water meters and pass the records to the XML DOM object
                    xdWaterMeters.Load(fsWaterMeters)
                    rem Create an XmlNodeList list of water meters using XPath
                    dim xnlWaterMeters  as XmlNodeList = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;

                    rem Check each node of the XML record
                    for each xnWaterMeter  as XmlNode in xnlWaterMeters)
                        rem Get the values for the water meter.
    rem Create a sentence and display it in the Meter Details text box.
                        TxtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")"
                    next
                end using
            end if
        }
    }
}

In the Solution Explorer, below the Customers folder, double-click Central.cs
From the Toolbox, add two buttons to the form below the list view and on the right side of the Edit Customer Acount button

Change the characteristics of the new buttons as follows:

Control	(Name)	Other Properties
ListView	LvwCustomers
Button	BtnDeleteCustomerAcount	&Delete Customer Acount... Anchor: Bottom, Right
Button	BtnClose	&Close Anchor: Bottom, Right

Double-click the Delete Customer Account button
Return to the Central form of the water meters and double-click the Close button

Change the document as follows:

import System.Xml

namespace StellarWaterPoint1.Customers
{
    public partial class Central : Form
    {
        public Central()
        {
            InitializeComponent()
        }

        private sub ShowCustomers()
        {
            int i = 1;

            lvwCustomers.Items.Clear()

            XmlDocument xdCustomers = new XmlDocument()
            string? strCustomers = "C:\Stellar Water Point10\Customers.xml"

            FileInfo? fiCustomers = new FileInfo(strCustomers)

            if fiCustomers.Exists
                using  fsCustomers as FileStream= new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read)
                    xdCustomers.Load(fsCustomers)
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.ChildNodes;

                    for each xnCustomer as XmlNode  in xnlCustomers
                        dim lviCustomer as ListViewItem = new ListViewItem(CStr(i))

                        lviCustomer.SubItems.Add(xnCustomer.FirstChild!.InnerText)   rem Account #
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling!.InnerText)   rem Account Name
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling!.InnerText) rem Meter #
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling!.InnerText)   rem Account Type
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText)   rem Address
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.InnerText)   rem City
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText)   rem County
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText)   rem State
                        lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText) rem ZIP-Code

                        lvwCustomers.Items.Add(lviCustomer)

                        i = i + 1
                    next
                end using
            end if
        }

        private sub Central_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        {
            ShowCustomers()
        }

        private sub BtnCreateCustomerAccount_Click(sender As Object, e As EventArgs)
        {
            Create create = new Create()

            if create.ShowDialog() =MsgBoxResult.OK
                rem Make sure the user provides an account number for the new account. 
                rem If not, don't create the account.
                if string.IsNullOrEmpty(create.MtbAccountNumber.Text)
                    MsgBox("You must provide an account number for the new customer. " +
                                    "Otherwise, the account cannot be created.",
                                    MsgBoxStyle.OkOnly Or MsgBoxStyle.Information,
                                    "Stellar Water Point")

                    Exit Sub
                end if

                rem If the meter details text box is empty, it means the user didn't enter
                rem a meter number, in which case there is no water meter associated 
                rem with the account. The account cannot be created.
                if string.IsNullOrEmpty(create.TxtMeterDetails.Text)
                    MsgBox("You must enter a water meter to associate with a new customer's account.",
                                    MsgBoxStyle.OkOnly Or MsgBoxStyle.Information,
                                    "Stellar Water Point")

                    Exit Sub
                end if

                rem Create a FileInfo object that will be used to manage a file
                FileInfo? fiCustomers = nothing
                rem Start a Stream object that will be used to manage a file
                FileStream? fsCustomers = nothing
                rem Create an XML Dom
                XmlDocument xdCustomers = new XmlDocument()
                rem Declare a string variable for the file that contains a list of customers
                string? strCustomers = "C:\Stellar Water Point10\Customers.xml"

                rem Pass the file of customers to the FileInfo object that was started
                fiCustomers = new FileInfo(strCustomers)

                rem Find out whether that file was already created
                if fiCustomers.Exists
                    rem If that file was already created, open it through 
rem the Stream object that was previously initiated.
                    using (fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open,
                                                        FileAccess.Read, FileShare.Read))
                        rem Pass the Stream object to the XML Dom that was previously created.
                        xdCustomers.Load(fsCustomers)
                    end using
                else
                    rem If the file of customers was not created already, start by 
rem initializing the Stream object that was previously initiated.
                    using (fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Create, FileAccess.Write, FileShare.Write))
                        rem Create a root to start the XML file
                        xdCustomers.LoadXml("<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
                                            "<customers></customers>")
                        rem Once the file has been started, save it
                        xdCustomers.Save(fsCustomers)
                    end using
                end if

                rem Now that we have an XML file for customers, open it
                using (fsCustomers = new FileStream(fiCustomers.FullName, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.ReadWrite)
                    rem We want to create an XML element to be added to the XML file.
                    rem To start, create an XML element named "customer".
                    XmlElement xeCustomer = xdCustomers.CreateElement("customer")

                    rem Create/Format the child nodes of the "customer" element
                    xeCustomer.InnerXml = "<account-number>" + create.MtbAccountNumber.Text + "</account-number>" +
                                          "<account-name>" + create.TxtAccountName.Text + "</account-name>" +
                                          "<meter-number>" + create.MtbMeterNumber.Text + "</meter-number>" +
                                          "<account-type>" + create.cbxAccountsTypes.Text + "</account-type>" +
                                          "<address>" + create.TxtAddress.Text + "</address>" +
                                          "<city>" + create.TxtCity.Text + "</city>" +
                                          "<county>" + create.TxtCounty.Text + "</county>" +
                                          "<state>" + create.TxtState.Text + "</state>" +
                                          "<zip-code>" + create.MtbZIPCode.Text + "</zip-code>"
                    xdCustomers.DocumentElement!.AppendChild(xeCustomer)
                    xdCustomers.Save(fsCustomers)
                end using
            end if

            ShowCustomers()
        end sub

        private sub ViewCustomerAccount_Click(sender As Object, e As EventArgs)
        {
            Details det = new Details()

            det.ShowDialog()
        }

        private sub BtnEditWaterMeter_Click(sender As Object, e As EventArgs)
        {
            rem This is the form that will be used to update a customer record
            Editor editor = new()
            rem Create an XML DOM object
            XmlDocument xdCustomers = new XmlDocument()
            rem Prepare the path and name of the file that holds a list of customers 
            string? strCustomers = "C:\Stellar Water Point10\Customers.xml"

            rem Display the Editor form.
            rem Find out if the user clicked the Update Customer Account button when closing the Editor dialog box.
            if editor.ShowDialog() =MsgBoxResult.OK
                rem Get the customers records and store them in the above XML DOM object
                xdCustomers.Load(strCustomers)

                rem Create an XmlNodeList list that reprensents the XML elements from the list of customers.
                rem Call the XML DOM's GetElementsByTagName() method. 
                rem To use the account number elements as references, pass the name of the Account # element as argument.
                XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.GetElementsByTagName("account-number")

                rem Visit each XML element of the list of customers
                for each xnCustomer as XmlNode  in xnlCustomers
                    rem When you get to an element, find out if the value of it Account Number is 
                    rem the same as the account number the user typed in the form. If that's the case, 
                    rem change the value of each node of that element, using the values from the form.
                    if xnCustomer.InnerText.Contains(editor.MtbAccountNumber.Text))
                        xnCustomer.ParentNode!.InnerXml = "<account-number>" + editor.MtbAccountNumber.Text + "</account-number>" +
                                              "<account-name>" + editor.TxtAccountName.Text + "</account-name>" +
                                              "<meter-number>" + editor.MtbMeterNumber.Text + "</meter-number>" +
                                              "<account-type>" + editor.cbxAccountsTypes.Text + "</account-type>" +
                                              "<address>" + editor.TxtAddress.Text + "</address>" +
                                              "<city>" + editor.TxtCity.Text + "</city>" +
                                              "<county>" + editor.TxtCounty.Text + "</county>" +
                                              "<state>" + editor.TxtState.Text + "</state>" +
                                              "<zip-code>" + editor.MtbZIPCode.Text + "</zip-code>"

                        rem After updating the elements, save the updated file
                        xdCustomers.Save(strCustomers)
                        rem After saving the file, stop searching
                        Exit For
                    end if
                next
            end if

            rem Now that the user has closed the Editor dialog box (and probably updated the XML file), 
            rem redisplay the list of customers.*/
            ShowCustomers()
        }

        private sub BtnDeleteCustomerAcount_Click(sender As Object, e As EventArgs)
        {
            rem Here is the dialog box that the user will use to locate and delete a customer account
            Delete delete = new()
            rem Create an XML DOM object
            XmlDocument xdCustomers = new XmlDocument()
            rem Specify the file that holds a database of customers
            string? strCustomers = "C:\Stellar Water Point10\Customers.xml"

            rem Open the Delete dialog box.
            rem Find out if the user clicked the Delete Customer Account button to close the Delete dialog box.
            if delete.ShowDialog() =MsgBoxResult.OK)
            {
                rem If there is no file for the list of customers, don't do nothing
                if !File.Exists(strCustomers))
                {
                    MsgBox("There is no file for the customers accounts in the system.",
                                    "Stellar Water Point",
                                    MsgBoxStyle.OkOnly Or MsgBoxStyle.Information)
                    Exit Sub
                }
                rem If the user didn't provide a valid account number, don't do nothing
                if string.IsNullOrEmpty(delete.MtbAccountNumber.Text))
                {
                    MsgBox("You must type an account number for the customer whose account you want to delete one.",
                                    "Stellar Water Point", MsgBoxStyle.OkOnly Or MsgBoxStyle.Information)
                    Exit Sub
                }

                rem Open the file of customers records and put those records in our XML DOM object
                xdCustomers.Load(strCustomers)

                rem Create an XmlNodeList list of the customers records. 
                rem Use the Account Number node as reference.
                XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.GetElementsByTagName("account-number")

                rem Check each customer record as an XML element
                for each xnCustomer as XmlNode  in xnlCustomers
                {
                    rem When you reach an element, find out whether its value is 
                    rem the same as the account number the user typed on the form.
                    if xnCustomer.InnerText=delete.MtbAccountNumber.Text)
                    {
                        rem If you find a matching record, find whether the user really wants to delete the record.
                        if MsgBox("Are you sure you want to remove this customer's account from the system?",
                                        "Stellar Water Point",
                                        MessageBoxButtons.YesNo, MessageBoxIcon.Question) =MsgBoxResult.Yes)
                        {
                            rem If the user really wants to delete the record, delete it...
                            xdCustomers.DocumentElement.RemoveChild(xnCustomer.ParentNode!)
                            rem and stop searching
                            Exit For
                        }
                    }
                }

                rem After removing the record, save the new version of the file 
                xdCustomers.Save(strCustomers)
            }

            rem Now that the user has closed the Delete dialog box (and probably deleted the XML file), 
            rem redisplay the list of customers.*/
            ShowCustomers()
        }

        private sub BtnClose_Click(sender As Object, e As EventArgs)
        {
            Close()
        }
    }
}

To execute the application, on the main menu, click Debug -> Start Without Debugging:
On the Central form, click the Customers button:
On the Central form of the customers, click the Delete Customer Account button:
In the Account # text box, type 7080-583-5947
Click the Find Customer Account button:
Click the Delete Customer Account button
Read the text on the message box.
On the message box, click Yes
Close the forms and return to your programming environment
From the Windows Explorer, open the Customers.xml file
Replace the content of the file with the provided file
Save the file
Return to your programming environment

Water Bills

Introduction

A water bill is a summary that indicates how much water a customer consumed and the value of that consumption. Our application will include the forms necessary to process water bills operations.

Practical Learning: Preparing Bills

In the Solution Explorer, right-click StellarWaterPoint1 -> Add -> New Folder
Type WaterBills as the name of the folder

A List of Water Bills

A water bill must contain as much information as possible. In our application, when displaying a list of water bills, we will show only select pieces of information.

Practical Learning: Viewing Water Bills

To create a form, in the Solution Explorer, right-click WaterBills -> Add -> Form (Windows Forms)...
Type Central
Click Add
In the Toolbox, click the ListView button and click the form

In the Properties window, change the characteristics of the list view as follows:

Control	(Name)	Text	Other Properties
ListView	LvwWaterBills		FullRowSelect: True GridLines: True View: Details Anchor: Top, Bottom, Left, Right
Button	BtnCreateWaterBill	Close	&Create Water Bill...

On the form, right-click the list view and click Edit Columns...

Create the columns as follows:

(Name)	Text	TextAlign	Width
colWaterBillId	Id		40
colBillNumber	Bill #	Center	80
colAccountNumber	Account #	Center	150
colStartDate	Start Date	Center	150
colEndDate	End Date	Center	150
colBillingDays	Days	Center
colCounterStart	Counter Start	Right	125
colCounterEnd	Counter End	Right	125
colTotalHCF	Total HCF	Right	100
colGallons	Gallons	Right	80
colPaymentDueDate	Pmt Due Date	Center	125
colAmountDue	Amt Due	Right	90

Click OK
Doubte-click an unoccupied area of the form to generate its Load event

Change the document as follows:

import System.Xml

namespace StellarWaterPoint1.WaterBills
{
    public partial class Central : Form
    {
        public Central()
        {
            InitializeComponent()
        }

        private sub ShowWaterBills()
        {
            lvwWaterBills.Items.Clear()

            XmlDocument xdWaterBills = new XmlDocument()
            string? strWaterBills = "C:\Stellar Water Point10\WaterBills.xml"

            FileInfo? fiWaterBills = new FileInfo(strWaterBills)

            if fiWaterBills.Exists)
            {
                using (FileStream? fsWaterBills = new FileStream(fiWaterBills.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterBills.Load(fsWaterBills)
                    XmlNodeList xnlWaterBills = xdWaterBills.DocumentElement!.ChildNodes;

                    int i = 1;

                    foreach (XmlNode xnWaterBill in xnlWaterBills)
                    {
                        ListViewItem lviWaterBill = new ListViewItem(i.ToString())

                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild!.InnerText)
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling!.InnerText)
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling!.InnerText)
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling!.InnerText)
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText)
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.InnerText)
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText)
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText)
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText.ToString())
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText)
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText)

                        lvwWaterBills.Items.Add(lviWaterBill)

                        i++;
                    }
                }
            }
        }

        private sub Central_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        {
            ShowWaterBills()
        }
    }
}

Return to the Water Bills form and double-click the Create Water Bill button

Implement the event as follows:

import System.Xml

namespace StellarWaterPoint1.WaterBills
{
    public partial class Central : Form
    {
        public Central()
        {
            InitializeComponent()
        }

        private sub ShowWaterBills()
        {
            lvwWaterBills.Items.Clear()

            XmlDocument xdWaterBills = new XmlDocument()
            string? strWaterBills = "C:\Stellar Water Point10\WaterBills.xml"

            FileInfo? fiWaterBills = new FileInfo(strWaterBills)

            if fiWaterBills.Exists)
            {
                using (FileStream? fsWaterBills = new FileStream(fiWaterBills.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterBills.Load(fsWaterBills)
                    XmlNodeList xnlWaterBills = xdWaterBills.DocumentElement!.ChildNodes;

                    int i = 1;

                    foreach (XmlNode xnWaterBill in xnlWaterBills)
                    {
                        ListViewItem lviWaterBill = new ListViewItem(i.ToString())

                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild!.InnerText)   rem Water Bill #
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling!.InnerText)   rem Account Number
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling!.InnerText) rem Meter Reading Start Date
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling!.InnerText)   rem Meter Reading End Date
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText) rem Billing Days
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.InnerText)  rem Counter Reading Start
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText)   rem Counter Reading End
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText)   rem Total CCF
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText.ToString())   rem Gallons
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText)   rem Payment Due Date
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText)  rem Amount Due

                        lvwWaterBills.Items.Add(lviWaterBill)

                        i++;
                    }
                }
            }
        }

        private sub Central_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        {
            ShowWaterBills()
        }

        private sub BtnCreateWaterBill_Click(sender As Object, e As EventArgs)
        {
            Create create = new()

            create.ShowDialog()

            ShowWaterBills()
        }
    }
}

In the Solution Explorer, double-click WaterDistribution.cs to open the main form of the application
From the Toolbox, add a button to the form

Using the the Properties window, change the characteristics of the button as follows:

Control	(Name)	Text	Font
Button	BtnWaterBills	Water &Bills...	Times New Roman, 24pt, style=Bold
Button	BtnClose	&Close	Times New Roman, 24pt, style=Bold

Double-click the Water &Bills button
Return to the Water Distribution form and double-click the Close button

Change the document as follows:

namespace StellarWaterPoint1
{
    public partial class WaterDistribution : Form
    {
        public WaterDistribution()
        {
            InitializeComponent()
        }

        private sub WaterDistribution_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        {
            rem If the directory for the database doesn't yet exist, create it
            Directory.CreateDirectory("C:\Stellar Water Point10")
        }

        private sub BtnWaterBills_Click(sender As Object, e As EventArgs)
        {
            WaterBills.Central central = new()

            central.Show()
        }

        private sub BtnCustomers_Click(sender As Object, e As EventArgs)
        {
            Customers.Central central = new Customers.Central()

            central.ShowDialog()
        }

        private sub BtnWaterMeters_Click(sender As Object, e As EventArgs)
        {
            WaterMeters.Central central = new WaterMeters.Central()

            central.ShowDialog()
        }

        private sub BtnClose_Click(sender As Object, e As EventArgs)
        {
            Close()
        }
    }
}

A Water Bill

A water bill is a collection of information that includes the identification of the customer who consumed the water, the period during which water was consumed, how much water was consumed, how much that consumption is worth, etc. We will create a form hat a user can use to create and process a water bill.

Practical Learning: Processing a Water Bill

To create a form, in the Solution Explorer, right-click WaterBills -> Add -> Form (Windows Forms)...
Type Create as the name of the file
Click Add

Design the form as follows:

Stellar Water Point - New Water Bill

Control	(Name)	Text	Other Properties
Label		Water Bill #:
TextBox	TxtBillNumber
GroupBox		Customer Information
Label		Account #:
MaskedTextBox	MtbAccountNumber		Masked: 0000-000-0000
Button	BtnFindCustomerAccount	Find Customer Account
Label		Customer Name:
TextBox	TxtCustomerName
Label		Address:
TextBox	TxtAddress
TextBox	TxtCity
TextBox	TxtCounty
TextBox	TxtState
MaskedTextBox	MtbZIPCode		Masked: Zip-Code
Label		______________________________________________
Label		Meter Details:
TextBox	TxtMeterDetails	Modifiers: Public
GroupBox		Meter Reading
Label		Meter Reading Start Date:
DateTimePicker	dtpMeterReadingStartDate
Label		Meter Reading End Date:
DateTimePicker	dtpMeterReadingEndDate
Label		Counter Reading Start:
TextBox	TxtCounterReadingStart
Label		Counter Reading End:
TextBox	TxtCounterReadingEnd
Button	BtnEvaluateWaterBill	Evaluate Water Bill
GroupBox		Meter Result
Label		Billing Days:
TextBox	TxtBillingDays		TextAlign: Right
Label		Total Gallons:
TextBox	TxtTotalGallons		TextAlign: Right
Label		Total CCF:
TextBox	TxtTotalCCF		TextAlign: Right
Label		First Tier Consumption:
TextBox	TxtFirstTierConsumption		TextAlign: Right
Label		Second Tier:
TextBox	TxtSecondTierConsumption		TextAlign: Right
Label		Last Tier:
TextBox	TxtLastTierConsumption		TextAlign: Right
GroupBox		Consumption Charges
Label		Water Charges:
TextBox	TxtWaterCharges		TextAlign: Right
Label		Sewer Charges:
TextBox	TxtSewerCharges		TextAlign: Right
Label		Environment Charges:
TextBox	TxtEnvironmentCharges		TextAlign: Right
Label		Total Charges:
TextBox	TxtTotalCharges		TextAlign: Right
GroupBox		Taxes
Label		Local Taxes:
TextBox	TxtLocalTaxes		TextAlign: Right
Label		State Taxes:
TextBox	TxtStateTaxes		TextAlign: Right
GroupBox		Water Bill Payment
Label		Payment Due Date:
DateTimePicker	dtpPaymentDueDate
Label		Amount Due:
TextBox	TxtAmountDue		TextAlign: Right
Label		Late Payment Due Date:
DateTimePicker	dtpLatePaymentDueDate
Label		Late Amount Due:
TextBox	TxtLateAmountDue		TextAlign: Right
Button	BtnSaveWaterBill	Save Water Bill
Button	BtnClose	Close

On the form, double-click the Find Customer Account button

Change the document as follows:

import System.Xml

namespace StellarWaterPoint1.WaterBills
{
    public partial class Create : Form
    {
        public Create()
        {
            InitializeComponent()
        }

        private sub BtnFindCustomerAccount_Click(sender As Object, e As EventArgs)
        {
            XmlDocument xdCustomers = new XmlDocument()
            string? strCustomers    = "C:\Stellar Water Point10\Customers.xml"

            FileInfo? fiCustomers   = new FileInfo(strCustomers)

            string strMeterNumber   = string.Empty;

            if fiCustomers.Exists)
            {
                using  fsCustomers as FileStream= new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdCustomers.Load(fsCustomers)
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + MtbAccountNumber.Text + "']")!;

                    for each xnCustomer as XmlNode  in xnlCustomers
                    {
                        TxtAccountName.Text = xnCustomer.NextSibling.InnerText
                        strMeterNumber      = xnCustomer.NextSibling.NextSibling.InnerText
                        TxtAccountType.Text = xnCustomer.NextSibling.NextSibling.NextSibling.InnerText
                        TxtAddress.Text     = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.InnerText
                        TxtCity.Text        = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.InnerText
                        TxtCounty.Text      = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtState.Text       = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtZIPCode.Text     = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                    }
                }
            }

            dim xdWaterMeters as XmlDocument = new XmlDocument()
            dim strWaterMeters as string= "C:\Stellar Water Point10\WaterMeters.xml"

            dim fiWaterMeters as FileInfo= new FileInfo(strWaterMeters)

            if fiWaterMeters.Exists)
            {
                using  fsWaterMeters as FileStream= new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterMeters.Load(fsWaterMeters)
                    dim xnlWaterMeters  as XmlNodeList = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;

                    for each xnWaterMeter  as XmlNode in xnlWaterMeters)
                    {
                        TxtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")"
                    }
                }
            }
        }
    }
}

Return to the Water Bills - Create form and double-click the Meter Reading End Date date time picker

Implement the event as follows:

import System.Xml

namespace StellarWaterPoint1.WaterBills
{
    public partial class Create : Form
    {
        public Create()
        {
            InitializeComponent()
        }

        private sub BtnFindCustomerAccount_Click(sender As Object, e As EventArgs)
        {
            . . .
        }

        private sub dtpMeterReadingEndDate_ValueChanged(sender As Object, e As EventArgs)
        {
            TimeSpan tsDays = dtpMeterReadingEndDate.Value - dtpMeterReadingStartDate.Value;

            TxtBillingDays.Text = (tsDays.Days + 1).ToString()
        }
    }
}

Return to the Water Bills - Create form and double-click the Evaluate Water Bill button

Implement the event as follows:

import System.Xml

namespace StellarWaterPoint1.WaterBills
{
    public partial class Create : Form
    {
        public Create()
        {
            InitializeComponent()
        }

        private sub BtnFindCustomerAccount_Click(sender As Object, e As EventArgs)
        {
            . . .
        }

        private sub dtpMeterReadingEndDate_ValueChanged(sender As Object, e As EventArgs)
        {
            . . .
        }

        (double a, double b, double c) CalculateTiers(string acnt, double total)
        {
            (double tier1, double tier2, double tier3) results = (0.00, 0.00, 0.00)

            switch (acnt)
            {
                case "RES":
                    results.tier1 = total * 41.50 / 10000.00;
                    results.tier2 = total * 32.50 / 10000.00;
                    results.tier3 = total * 26.00 / 10000.00;
                    Exit For
                case "SGO":
                    results.tier1 = total * 46 / 10000;
                    results.tier2 = total * 50 / 10000;
                    results.tier3 = total * 4 / 10000;
                    Exit For
                case "BUS":
                    results.tier1 = total * 45 / 10000;
                    results.tier2 = total * 30 / 10000;
                    results.tier3 = total * 25 / 10000;
                    Exit For
                case "UUO":
                    results.tier1 = total * 25 / 10000;
                    results.tier2 = total * 35 / 10000;
                    results.tier3 = total * 40 / 10000;
                    Exit For
                case "WAT":
                    results.tier1 = total * 50 / 10000;
                    results.tier2 = total * 40 / 10000;
                    results.tier3 = total * 10 / 10000;
                    Exit For
                default:
                    results.tier1 = total * (48.00 / 10000.00)
                    results.tier2 = total * (32.00 / 10000.00)
                    results.tier3 = total * (20.00 / 10000.00)
                    Exit For
            }

            return results;
        }

        private double CalculateSewerCharges(string acnt, double total)
        {
            double result;

            if acnt="RES")
            {
                result = total * 6.826941 / 100;
            }
            else if acnt="SGO")
            {
                result = total * 4.162522 / 100;
            }
            else if acnt="BUS")
            {
                result = total * 8.3136 / 100;
            }
            else if acnt="UUO")
            {
                result = total * 10.6247 / 100;
            }
            else if acnt="WAT")
            {
                result = total * 12.0535 / 100;
            }
            else rem if acnt="OTH)"
            {
                result = total * 9.2065 / 100;
            }

            return result;
        }

        private double CalculateEnvironmentCharges(string acnt, double total)
        {
            double result;

            switch(acnt)
            {
                case "RES":
                    result = total * 0.022724;
                    Exit For
                case "SGO":
                    result = total * 0.118242;
                    Exit For
                case "BUS":
                    result = total * 0.161369;
                    Exit For
                case "UUO":
                    result = total * 0.082477;
                    Exit For
                case "WAT":
                    result = total * 0.413574;
                    Exit For
                default:
                    result = total * 0.221842;
                    Exit For
            }

            return result;
        }

        private double CalculateServiceCharges(string acnt, double total)
        {
            switch (acnt)
            {
                case "RES":
                    return total * 0.145748;
                case "SGO":
                    return total * 0.102246;
                case "BUS":
                    return total * 0.242627;
                case "UUO":
                    return total * 0.186692;
                case "WAT":
                    return total * 0.412628;
                default:
                    return total * 0.210248;
            }
        }

        private double CalculateLocalTaxes(string acnt, double total) => acnt switch
        {
            "RES" => total * 0.031574,
            "SGO" => total * 0.035026,
            "BUS" => total * 0.122517,
            "UUO" => total * 0.105737,
            "WAT" => total * 0.153248,
            _ => total * 0.125148
        };

        private double CalculateStateTaxes(string acnt, double total) => acnt switch
        {
            "RES" => total * 0.016724,
            "SGO" => total * 0.008779,
            "BUS" => total * 0.042448,
            "UUO" => total * 0.067958,
            "WAT" => total * 0.081622,
            _ => total * 0.013746
        };

        private DateTime SetPaymentDueDate(string acnt, DateTime date)
        
            TimeSpan tsPaymentDueDate = new TimeSpan(1, 0, 0, 0)

            if acnt="RES"
                tsPaymentDueDate = new TimeSpan(15, 0, 0, 0)
            }
            else if acnt="SGO")
            
                tsPaymentDueDate = new TimeSpan(20, 0, 0, 0)
            }
            else if acnt="BUS")
            
                tsPaymentDueDate = new TimeSpan(30, 0, 0, 0)
            }
            else if acnt="UUO")
            
                tsPaymentDueDate = new TimeSpan(15, 0, 0, 0)
            }
            else if acnt="WAT")
            
                tsPaymentDueDate = new TimeSpan(40, 0, 0, 0)
            }
            else
            
                tsPaymentDueDate = new TimeSpan(35, 0, 0, 0)
            }

            return date + tsPaymentDueDate;
        }

        private DateTime SetLatePaymentDueDate(string acnt, DateTime date)
        
            switch (acnt)
            
                case "RES":
                    return date + new TimeSpan(30, 0, 0, 0)
                case "SGO":
                    return date + new TimeSpan(40, 0, 0, 0)
                case "BUS":
                    return date + new TimeSpan(50, 0, 0, 0)
                case "UUO":
                    return date + new TimeSpan(60, 0, 0, 0)
                case "WAT":
                    return date + new TimeSpan(65, 0, 0, 0)
                default:
                    return date + new TimeSpan(45, 0, 0, 0)
            }
        }

        private double CalculateLateAmountDue(string acnt, double amt) => acnt switch
        
            "RES" => amt + 8.95,
            "SGO" => amt + (amt / 4.575),
            "BUS" => amt + (amt / 12.315),
            "UUO" => amt + (amt / 7.425),
            "WAT" => amt + (amt / 15.225),
            _     => amt + (amt / 6.735)
        };

        private sub BtnEvaluateWaterBill_Click(sender As Object, e As EventArgs)
        
            double counterStart = 0, counterEnd = 0;

            try
            
                counterStart = double.Parse(TxtCounterReadingStart.Text)
            }
            catch (FormatException feCRStart)
            
                MsgBox("There was a problem with the value of the " +
                                "Counter Reading Start. The error produced is: " + feCRStart.Message,
                                "Stellar Water Point", MsgBoxStyle.OkOnly Or MsgBoxStyle.Information)
            }

            try
            
                counterEnd = double.Parse(TxtCounterReadingEnd.Text)
            }
            catch (FormatException feCREnd)
            
                MsgBox("There was a problem with the value of the " +
                                "Counter Reading End. The error produced is: " + feCREnd.Message,
                                "Stellar Water Point", MsgBoxStyle.OkOnly Or MsgBoxStyle.Information)
            }

            double consumption            = counterEnd - counterStart;
            double gallons                = consumption * 748.05;

            string strAccountType         = TxtAccountType.Text[..3];

            (double first, double second, double last) tiers = CalculateTiers(strAccountType, gallons)

            double waterCharges           = tiers.first + tiers.second + tiers.last;
            double sewerCharges           = CalculateSewerCharges(strAccountType, waterCharges)
            double envCharges             = CalculateEnvironmentCharges(strAccountType, waterCharges)
            double srvCharges             = CalculateServiceCharges(strAccountType, waterCharges)
            double totalCharges           = waterCharges + sewerCharges + envCharges + srvCharges;
            double localTaxes             = CalculateLocalTaxes(strAccountType, waterCharges)
            double stateTaxes             = CalculateStateTaxes(strAccountType, waterCharges)
            double amtDue                 = totalCharges + localTaxes + stateTaxes;

            TxtTotalHCF.Text              = consumption.ToString()
            TxtTotalGallons.Text          = ((int)(Math.Ceiling(gallons))).ToString()
            TxtFirstTierConsumption.Text  = tiers.first.ToString("F")
            TxtSecondTierConsumption.Text = tiers.second.ToString("F")
            TxtLastTierConsumption.Text   = tiers.last.ToString("F")
            TxtWaterCharges.Text          = waterCharges.ToString("F")
            TxtSewerCharges.Text          = sewerCharges.ToString("F")
            TxtEnvironmentCharges.Text    = envCharges.ToString("F")
            TxtServiceCharges.Text        = srvCharges.ToString("F")
            TxtTotalCharges.Text          = totalCharges.ToString("F")
            TxtLocalTaxes.Text            = localTaxes.ToString("F")
            TxtStateTaxes.Text            = stateTaxes.ToString("F")
            dtpPaymentDueDate.Value       = SetPaymentDueDate(strAccountType, dtpMeterReadingEndDate.Value)
            TxtAmountDue.Text             = amtDue.ToString("F")
            dtpLatePaymentDueDate.Value   = SetLatePaymentDueDate(strAccountType, dtpMeterReadingEndDate.Value)
            TxtLateAmountDue.Text         = CalculateLateAmountDue(strAccountType, amtDue).ToString("F")
        }
    }
}

Return to the Water Bills - Create form and double-click the Save Water Bill button
Return to the form and double-click the Close button

Finalize the document as follows:

import System.Xml

namespace StellarWaterPoint1.WaterBills

    public partial class Create : Form
    
        public Create()
        
            InitializeComponent()
        }

        private sub BtnFindCustomerAccount_Click(sender As Object, e As EventArgs)
        
            XmlDocument xdCustomers = new XmlDocument()
            string? strCustomers    = "C:\Stellar Water Point10\Customers.xml"

            FileInfo? fiCustomers   = new FileInfo(strCustomers)

            string strMeterNumber   = string.Empty;

            if fiCustomers.Exists)
            
                using  fsCustomers as FileStream= new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                
                    xdCustomers.Load(fsCustomers)
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + MtbAccountNumber.Text + "']")!;

                    for each xnCustomer as XmlNode  in xnlCustomers
                    
                        TxtAccountName.Text = xnCustomer.NextSibling.InnerText
                        strMeterNumber      = xnCustomer.NextSibling.NextSibling.InnerText
                        TxtAccountType.Text = xnCustomer.NextSibling.NextSibling.NextSibling.InnerText
                        TxtAddress.Text     = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.InnerText
                        TxtCity.Text        = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.InnerText
                        TxtCounty.Text      = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtState.Text       = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtZIPCode.Text     = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                    }
                }
            }

            dim xdWaterMeters as XmlDocument = new XmlDocument()
            dim strWaterMeters as string= "C:\Stellar Water Point10\WaterMeters.xml"

            dim fiWaterMeters as FileInfo= new FileInfo(strWaterMeters)

            if fiWaterMeters.Exists)
            
                using  fsWaterMeters as FileStream= new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                
                    xdWaterMeters.Load(fsWaterMeters)
                    dim xnlWaterMeters  as XmlNodeList = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;

                    for each xnWaterMeter  as XmlNode in xnlWaterMeters)
                    
                        TxtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")"
                    }
                }
            }
        }

        private sub dtpMeterReadingEndDate_ValueChanged(sender As Object, e As EventArgs)
        
            TimeSpan tsDays = dtpMeterReadingEndDate.Value - dtpMeterReadingStartDate.Value;

            TxtBillingDays.Text = (tsDays.Days + 1).ToString()
        }

        (double a, double b, double c) CalculateTiers(string acnt, double total)
        
            (double tier1, double tier2, double tier3) results = (0.00, 0.00, 0.00)

            if acnt="RES")
            
                results.tier1 = total * 41.50 / 10000.00;
                results.tier2 = total * 32.50 / 10000.00;
                results.tier3 = total * 26.00 / 10000.00;
            }
            else if acnt="SGO")
            
                results.tier1 = total * 46 / 10000;
                results.tier2 = total * 50 / 10000;
                results.tier3 = total *  4 / 10000;
            }
            else if acnt="BUS")
            
                results.tier1 = total * 45 / 10000;
                results.tier2 = total * 30 / 10000;
                results.tier3 = total * 25 / 10000;
            }
            else if acnt="UUO")
            
                results.tier1 = total * 25 / 10000;
                results.tier2 = total * 35 / 10000;
                results.tier3 = total * 40 / 10000;
            }
            else if acnt="WAT")
            
                results.tier1 = total * 50 / 10000;
                results.tier2 = total * 40 / 10000;
                results.tier3 = total * 10 / 10000;
            }
            else
            
                results.tier1 = total * (48.00 / 10000.00)
                results.tier2 = total * (32.00 / 10000.00)
                results.tier3 = total * (20.00 / 10000.00)
            }

            return results;
        }

        private double CalculateSewerCharges(string acnt, double total)
        
            double result;

            if acnt="RES")
            
                result = total * 6.826941 / 100;
            }
            else if acnt="SGO")
            
                result = total * 4.162522 / 100;
            }
            else if acnt="BUS")
            
                result = total * 8.3136 / 100;
            }
            else if acnt="UUO")
            
                result = total * 10.6247 / 100;
            }
            else if acnt="WAT")
            
                result = total * 12.0535 / 100;
            }
            else rem if acnt="OTH)"
            
                result = total * 9.2065 / 100;
            }

            return result;
        }

        private double CalculateEnvironmentCharges(string acnt, double total)
        
            double result;

            switch(acnt)
            
                case "RES":
                    result = total * 0.022724;
                    Exit For
                case "SGO":
                    result = total * 0.118242;
                    Exit For
                case "BUS":
                    result = total * 0.161369;
                    Exit For
                case "UUO":
                    result = total * 0.082477;
                    Exit For
                case "WAT":
                    result = total * 0.413574;
                    Exit For
                default:
                    result = total * 0.221842;
                    Exit For
            }

            return result;
        }

        private double CalculateServiceCharges(string acnt, double total)
        
            switch (acnt)
            
                case "RES":
                    return total * 0.145748;
                case "SGO":
                    return total * 0.102246;
                case "BUS":
                    return total * 0.242627;
                case "UUO":
                    return total * 0.186692;
                case "WAT":
                    return total * 0.412628;
                default:
                    return total * 0.210248;
            }
        }

        private double CalculateLocalTaxes(string acnt, double total) => acnt switch
        
            "RES" => total * 0.031574,
            "SGO" => total * 0.035026,
            "BUS" => total * 0.122517,
            "UUO" => total * 0.105737,
            "WAT" => total * 0.153248,
            _ => total * 0.125148
        };

        private double CalculateStateTaxes(string acnt, double total) => acnt switch
        
            "RES" => total * 0.016724,
            "SGO" => total * 0.008779,
            "BUS" => total * 0.042448,
            "UUO" => total * 0.067958,
            "WAT" => total * 0.081622,
            _ => total * 0.013746
        };

        private DateTime SetPaymentDueDate(string acnt, DateTime date)
        
            TimeSpan tsPaymentDueDate = new TimeSpan(1, 0, 0, 0)

            if acnt="RES")
            
                tsPaymentDueDate = new TimeSpan(15, 0, 0, 0)
            }
            else if acnt="SGO")
            
                tsPaymentDueDate = new TimeSpan(20, 0, 0, 0)
            }
            else if acnt="BUS")
            {
                tsPaymentDueDate = new TimeSpan(30, 0, 0, 0)
            }
            else if acnt="UUO")
            {
                tsPaymentDueDate = new TimeSpan(15, 0, 0, 0)
            }
            else if acnt="WAT")
            {
                tsPaymentDueDate = new TimeSpan(40, 0, 0, 0)
            }
            else
            {
                tsPaymentDueDate = new TimeSpan(35, 0, 0, 0)
            }

            return date + tsPaymentDueDate;
        }

        private DateTime SetLatePaymentDueDate(string acnt, DateTime date)
        {
            switch (acnt)
            {
                case "RES":
                    return date + new TimeSpan(30, 0, 0, 0)
                case "SGO":
                    return date + new TimeSpan(40, 0, 0, 0)
                case "BUS":
                    return date + new TimeSpan(50, 0, 0, 0)
                case "UUO":
                    return date + new TimeSpan(60, 0, 0, 0)
                case "WAT":
                    return date + new TimeSpan(65, 0, 0, 0)
                default:
                    return date + new TimeSpan(45, 0, 0, 0)
            }
        }

        private double CalculateLateAmountDue(string acnt, double amt) => acnt switch
        {
            "RES" => amt + 8.95,
            "SGO" => amt + (amt / 4.575),
            "BUS" => amt + (amt / 12.315),
            "UUO" => amt + (amt / 7.425),
            "WAT" => amt + (amt / 15.225),
            _     => amt + (amt / 6.735)
        };

        private sub BtnEvaluateWaterBill_Click(sender As Object, e As EventArgs)
        {
            double counterStart = 0, counterEnd = 0;

            try
            {
                counterStart = double.Parse(TxtCounterReadingStart.Text)
            }
            catch (FormatException feCRStart)
            {
                MsgBox("There was a problem with the value of the " +
                                "Counter Reading Start. The error produced is: " + feCRStart.Message,
                                "Stellar Water Point", MsgBoxStyle.OkOnly Or MsgBoxStyle.Information)
            }

            try
            {
                counterEnd = double.Parse(TxtCounterReadingEnd.Text)
            }
            catch (FormatException feCREnd)
            {
                MsgBox("There was a problem with the value of the " +
                                "Counter Reading End. The error produced is: " + feCREnd.Message,
                                "Stellar Water Point", MsgBoxStyle.OkOnly Or MsgBoxStyle.Information)
            }

            double consumption            = counterEnd - counterStart;
            double gallons                = consumption * 748.05;

            string strAccountType         = TxtAccountType.Text[..3];

            (double first, double second, double last) tiers = CalculateTiers(strAccountType, gallons)

            double waterCharges           = tiers.first + tiers.second + tiers.last;
            double sewerCharges           = CalculateSewerCharges(strAccountType, waterCharges)
            double envCharges             = CalculateEnvironmentCharges(strAccountType, waterCharges)
            double srvCharges             = CalculateServiceCharges(strAccountType, waterCharges)
            double totalCharges           = waterCharges + sewerCharges + envCharges + srvCharges;
            double localTaxes             = CalculateLocalTaxes(strAccountType, waterCharges)
            double stateTaxes             = CalculateStateTaxes(strAccountType, waterCharges)
            double amtDue                 = totalCharges + localTaxes + stateTaxes;

            TxtTotalHCF.Text              = consumption.ToString()
            TxtTotalGallons.Text          = ((int)(Math.Ceiling(gallons))).ToString()
            TxtFirstTierConsumption.Text  = tiers.first.ToString("F")
            TxtSecondTierConsumption.Text = tiers.second.ToString("F")
            TxtLastTierConsumption.Text   = tiers.last.ToString("F")
            TxtWaterCharges.Text          = waterCharges.ToString("F")
            TxtSewerCharges.Text          = sewerCharges.ToString("F")
            TxtEnvironmentCharges.Text    = envCharges.ToString("F")
            TxtServiceCharges.Text        = srvCharges.ToString("F")
            TxtTotalCharges.Text          = totalCharges.ToString("F")
            TxtLocalTaxes.Text            = localTaxes.ToString("F")
            TxtStateTaxes.Text            = stateTaxes.ToString("F")
            dtpPaymentDueDate.Value       = SetPaymentDueDate(strAccountType, dtpMeterReadingEndDate.Value)
            TxtAmountDue.Text             = amtDue.ToString("F")
            dtpLatePaymentDueDate.Value   = SetLatePaymentDueDate(strAccountType, dtpMeterReadingEndDate.Value)
            TxtLateAmountDue.Text         = CalculateLateAmountDue(strAccountType, amtDue).ToString("F")
        }

        private sub BtnSaveWaterBill_Click(sender As Object, e As EventArgs)
        {
            if string.IsNullOrEmpty(TxtBillNumber.Text))
            {
                MsgBox("You must type a bill number." +
                                "Otherwise, the account cannot be saved.",
                                "Stellar Water Point", MessageBoxButtons.OK)
                Exit Sub
            }

            if string.IsNullOrEmpty(TxtCounterReadingStart.Text))
            {
                MsgBox("You must enter the start value of the water bill counter." +
                                "Otherwise, the account cannot be saved.",
                                "Stellar Water Point", MessageBoxButtons.OK)
                Exit Sub
            }

            if string.IsNullOrEmpty(MtbAccountNumber.Text))
            {
                MsgBox("You must type an account number of a customer." +
                                "Otherwise, the account cannot be saved.",
                                "Stellar Water Point", MessageBoxButtons.OK)
                Exit Sub
            }

            FileStream? fsWaterBills = nothing
            XmlDocument xdWaterBills = new XmlDocument()
            string strWaterBills     = "C:\Stellar Water Point10\WaterBills.xml"

            FileInfo? fiWaterBills   = new FileInfo(strWaterBills)

            if fiWaterBills.Exists)
            {
                using (fsWaterBills = new FileStream(fiWaterBills.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterBills.Load(fsWaterBills)
                }
            }
            else
            {
                using (fsWaterBills = new FileStream(fiWaterBills.FullName, FileMode.Create, FileAccess.Write, FileShare.Write))
                {
                    xdWaterBills.LoadXml("<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
                                         "<water-bills></water-bills>")
                    xdWaterBills.Save(fsWaterBills)
                }
            }

            using (fsWaterBills = new FileStream(fiWaterBills.FullName, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.ReadWrite))
            {
                XmlElement xeWaterBill = xdWaterBills.CreateElement("water-bill")

                xeWaterBill.InnerXml = "<bill-number>"              + TxtBillNumber.Text + "</bill-number>" +
                                       "<account-number>"           + MtbAccountNumber.Text + "</account-number>" +
                                       "<meter-reading-start-date>" + dtpMeterReadingStartDate.Value.ToShortDateString() + "</meter-reading-start-date>" +
                                       "<meter-reading-end-date>"   + dtpMeterReadingEndDate.Value.ToShortDateString() + "</meter-reading-end-date>" +
                                       "<billing-days>"             + TxtBillingDays.Text + "</billing-days>" +
                                       "<counter-reading-start>"    + TxtCounterReadingStart.Text + "</counter-reading-start>" +
                                       "<counter-reading-end>"      + TxtCounterReadingEnd.Text + "</counter-reading-end>" +
                                       "<total-hcf>"                + TxtTotalHCF.Text + "</total-hcf>" +
                                       "<total-gallons>"            + TxtTotalGallons.Text + "</total-gallons>" +
                                       "<first-tier-consumption>"   + TxtFirstTierConsumption.Text + "</first-tier-consumption>" +
                                       "<second-tier-consumption>"  + TxtSecondTierConsumption.Text + "</second-tier-consumption>" +
                                       "<last-tier-consumption>"    + TxtLastTierConsumption.Text + "</last-tier-consumption>" +
                                       "<water-charges>"            + TxtWaterCharges.Text + "</water-charges>" +
                                       "<sewer-charges>"            + TxtSewerCharges.Text + "</sewer-charges>" +
                                       "<environment-charges>"      + TxtEnvironmentCharges.Text + "</environment-charges>" +
                                       "<service-charges>"          + TxtEnvironmentCharges.Text + "</service-charges>" +
                                       "<total-charges>"            + TxtTotalCharges.Text + "</total-charges>" +
                                       "<state-taxes>"              + TxtStateTaxes.Text + "</state-taxes>" +
                                       "<local-taxes>"              + TxtLocalTaxes.Text + "</local-taxes>" +
                                       "<payment-due-date>"         + dtpPaymentDueDate.Value.ToShortDateString() + "</payment-due-date>" +
                                       "<amount-due>"               + TxtAmountDue.Text + "</amount-due>" +
                                       "<late-payment-due-date>"    + dtpLatePaymentDueDate.Value.ToShortDateString() + "</late-payment-due-date>" +
                                       "<late-amount-due>"          + TxtLateAmountDue.Text + "</late-amount-due>"

                xdWaterBills.DocumentElement!.AppendChild(xeWaterBill)
                xdWaterBills.Save(fsWaterBills)
            }

            Close()
        }

        private sub BtnClose_Click(sender As Object, e As EventArgs)
        {
            Close()
        }
    }
}

In the Solution Explorer, in the WaterBills folder, double-click Central.cs
From the Toolbox, add a Button to the form

In the Properties window, change the characteristics of the button as follows:

Control	(Name)	Text	Other Properties
ListView	LvwWaterBills		No Change
Button	BtnCreateWaterBill	Close	&Create Water Bill...

Double-click the Create Water Bill button

Implement the event as follows:

private sub BtnProcessWaterBill_Click(sender As Object, e As EventArgs)
{
    Create create = new()

    create.ShowDialog()

    ShowWaterBills()
}

To execute the application, on the main menu, click Debug -> Start Without Debugging:
On the Water Distribution form, click the Water Bills button:
On the Water Bills form, click the Create Water Bill button:

Enter the following values in the indicated text boxes or select the date values. Then click Find Customer Account, followed by Evaluate Water Bill, followed by Save Water Bill:

Water Bill #	Account #	Reading Start Date	Reading End Date	Counter Reading Start	Counter Reading End
451474	2068-258-9486	01/11/2010	04/12/2010	103943	103956
923633	5293-957-3395	01/17/2010	08/18/2010	256945	256972
917829	9279-570-8394	02/15/2010	05/14/2010	5205	5222
202666	6986-829-3741	03/08/2010	06/06/2010	5679	5690

Close the forms and return to your programming environment

Details on a Wate Bill

Probably the simplest operation that a user can perform on a water bill to only view its details. To make this happen, we will create and provide a form.

Practical Learning: Creating a Water Meter Record

To create a form, in the Solution Explorer, right-click WaterBills -> Add -> Form (Windows Forms)...
For the Name of the form, type Details
Press Enter

Design the form as follows:

Stellar Water Point - New Customer Account

Control	(Name)	Text	Other Properties
Label		Water Bill #:
TextBox	TxtBillNumber
Button	BtnFindWaterBill	Find Water Bill
GroupBox		Customer Information
Label		Account #:
TextBox	TxtAccountNumber		Enabled: False
Label		Customer Name:
TextBox	TxtCustomerName		Enabled: False
Label		Address:
TextBox	TxtAddress		Enabled: False
TextBox	TxtCity		Enabled: False
TextBox	TxtCounty		Enabled: False
TextBox	TxtState		Enabled: False
TextBox	TxtZIPCode		Enabled: False
Label		_____________________________________
Label		Meter Details:
TextBox	TxtMeterDetails		Enabled: False
GroupBox		Meter Reading
Label		Meter Reading Start Date:
TextBox	TxtMeterReadingStartDate		Enabled: False
Label		Meter Reading End Date:
TextBox	TxtMeterReadingEndDate		Enabled: False
Label		Counter Reading Start:
TextBox	TxtCounterReadingStart		Enabled: False
Label		Counter Reading End:
TextBox	TxtCounterReadingEnd		Enabled: False
GroupBox		Meter Result
Label		Billing Days:
TextBox	TxtBillingDays		TextAlign: Right Enabled: False
Label		Total Gallons:
TextBox	TxtTotalGallons		TextAlign: Right Enabled: False
Label		Total CCF:
TextBox	TxtTotalHCF		TextAlign: Right Enabled: False
Label		First Tier Consumption:
TextBox	TxtFirstTierConsumption		TextAlign: Right Enabled: False
Label		Second Tier:
TextBox	TxtSecondTierConsumption		TextAlign: Right Enabled: False
Label		Last Tier:
TextBox	TxtLastTierConsumption		TextAlign: Right Enabled: False
GroupBox		Consumption Charges
Label		Water Charges:
TextBox	TxtWaterCharges		TextAlign: Right Enabled: False
Label		Sewer Charges:
TextBox	TxtSewerCharges		TextAlign: Right Enabled: False
Label		Environment Charges:
TextBox	TxtEnvironmentCharges		TextAlign: Right Enabled: False
Label		Total Charges:
TextBox	TxtTotalCharges		TextAlign: Right Enabled: False
GroupBox		Taxes
Label		Local Taxes:
TextBox	TxtLocalTaxes		TextAlign: Right Enabled: False
Label		State Taxes:
TextBox	TxtStateTaxes		TextAlign: Right Enabled: False
GroupBox		Water Bill Payment
Label		Payment Due Date:
TextBox	TxtPaymentDueDate		Enabled: False
Label		Amount Due:
TextBox	TxtAmountDue		TextAlign: Right Enabled: False
Label		Late Payment Due Date:
TextBox	TxtLatePaymentDueDate		Enabled: False
Label		Late Amount Due:
TextBox	TxtLateAmountDue		TextAlign: Right Enabled: False
Button	BtnClose	Close

Using the Properties window, change some characteristics of the form as follows:

FormBorderStyle: FixedDialog
Text:            Stellar Water Point - Water Bill Details
StartPosition:   CenterScreen
MinimizeBox:     False
MaximizeBox:     False

On the form, double-click the Find Water Bill button
Return to the form and double-click the Close button

Change the document as follows:

import System.Xml

namespace StellarWaterPoint1.WaterBills
{
    public partial class Details : Form
    {
        public Details()
        {
            InitializeComponent()
        }

        private sub BtnFindWaterBill_Click(sender As Object, e As EventArgs)
        {
            rem If the user clicks the Find Water Meter button, 
             * make sure there is an invoice number in the top text box.
            if string.IsNullOrEmpty(TxtBillNumber.Text))
            {
                MsgBox("You must provide a water bill number and then click the Find Water Bill button.",
                                "Stellar Water Point", MsgBoxStyle.OkOnly Or MsgBoxStyle.Information)
                rem If the user didn't type a bill number but clicked Find Water Bill, don't do anything
                Exit Sub
            }

            XmlDocument xdWaterBills = new XmlDocument()
            string? strWaterBills = "C:\Stellar Water Point10\WaterBills.xml"

            FileInfo? fiWaterBills = new FileInfo(strWaterBills)

            if fiWaterBills.Exists)
            {
                using (FileStream? fsWaterBills = new FileStream(fiWaterBills.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterBills.Load(fsWaterBills)

                    rem Use XPath to locate the water bill that has 
                     * the same invoice number as the one in the Water Bill Number text box.
                     * Store the water bill in an XmlNodeList variable.
                    XmlNodeList xnlWaterBills = xdWaterBills.DocumentElement!.SelectNodes("//bill-number[.='" + TxtBillNumber.Text + "']")!;

                    foreach (XmlNode xnWaterBill in xnlWaterBills)
                    {
                        TxtBillNumber.Text            =                xnWaterBill.FirstChild.InnerText
                        TxtAccountNumber.Text         =                xnWaterBill.NextSibling.InnerText
                        TxtMeterReadingStartDate.Text = DateTime.Parse(xnWaterBill.NextSibling.NextSibling!.InnerText).ToLongDateString()
                        TxtMeterReadingEndDate.Text   = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling!.InnerText).ToLongDateString()                        
                        TxtBillingDays.Text           =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling.InnerText
                        TxtCounterReadingStart.Text   =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling.InnerText                        
                        TxtCounterReadingEnd.Text     =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtTotalHCF.Text              =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtTotalGallons.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtFirstTierConsumption.Text  =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtSecondTierConsumption.Text =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtLastTierConsumption.Text   =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtWaterCharges.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtSewerCharges.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtEnvironmentCharges.Text    =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtServiceCharges.Text        =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtTotalCharges.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtStateTaxes.Text            =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtLocalTaxes.Text            =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtPaymentDueDate.Text        = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText).ToLongDateString()
                        TxtAmountDue.Text             =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtLatePaymentDueDate.Text    = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText).ToLongDateString()
                        TxtLateAmountDue.Text         =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                    }
                }
            }

            XmlDocument xdCustomers = new XmlDocument()
            rem Declare a variable for a file that holds the list of customers
            string? strCustomers = "C:\Stellar Water Point10\Customers.xml"

            rem Create a FileInfo object for the customers
            FileInfo? fiCustomers = new FileInfo(strCustomers)

            rem We will need to know the water meter associated with this customer account
            string strMeterNumber = string.Empty;

            rem Check whether the file that holds a list of customers exists
            if fiCustomers.Exists)
            {
                rem If that exists, open it and pass it to a FileStream object
                using  fsCustomers as FileStream= new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    rem Get the list of customers and pass the records to the XML DOM object created earlier
                    xdCustomers.Load(fsCustomers)
                    rem Create an XmlNodeList list of customers using XPath
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + TxtAccountNumber.Text + "']")!;

                    rem Check each node of the XML record and display its values in each Windows control on the form
                    for each xnCustomer as XmlNode  in xnlCustomers
                    {
                        //MtbAccountNumber.Text = xnCustomer.NextSibling.InnerText   rem Meter #
                        TxtAccountName.Text = xnCustomer.NextSibling.InnerText rem Account Name

                        strMeterNumber      = xnCustomer.NextSibling.NextSibling.InnerText   rem Meter Number
                        TxtAccountType.Text = xnCustomer.NextSibling.NextSibling.NextSibling.InnerText   rem Account Type
                        TxtAddress.Text     = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.InnerText   rem Address
                        TxtCity.Text        = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.InnerText   rem City
                        TxtCounty.Text      = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling.InnerText   rem County
                        TxtState.Text       = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText   rem State
                        TxtZIPCode.Text     = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText rem ZIP-Code
                    }
                }
            }

            rem Create an XML DOM object for the water meters records
            dim xdWaterMeters as XmlDocument = new XmlDocument()
            rem Declare a variable for a file that holds the list of water meters
            dim strWaterMeters as string= "C:\Stellar Water Point10\WaterMeters.xml"

            rem Create a FileInfo object for the customers
            dim fiWaterMeters as FileInfo= new FileInfo(strWaterMeters)

            rem Check whether the file that holds a list of water meters exists
            if fiWaterMeters.Exists)
            {
                rem Get the list of water meters and pass the records to the XML DOM object
                using  fsWaterMeters as FileStream= new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    rem Get the list of water meters and pass the records to the XML DOM object
                    xdWaterMeters.Load(fsWaterMeters)
                    rem Create an XmlNodeList list of water meters using XPath
                    dim xnlWaterMeters  as XmlNodeList = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;

                    rem Check each node of the XML record
                    for each xnWaterMeter  as XmlNode in xnlWaterMeters)
                    {
                        rem Get the values for the water meter.
                         * Create a sentence and display it in the Meter Details text box.
                        TxtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")"
                    }
                }
            }
        }

        private sub BtnClose_Click(sender As Object, e As EventArgs)
        {
            Close()
        }
    }
}

In the Solution Explorer, below the WaterBills folder, double-click Details.cs to open its form
From the Toolbox, add a button to the form below the list view and to the right of the Create Water Bill button

Change the characteristics of the button as follows:

Control		(Name)	Other Properties
Button		BtnViewWaterBill	&View Water Bill... Anchor: Bottom, Right

Double-click the View Water Bill button

Change the document as follows:

import System.Xml

namespace StellarWaterPoint1.WaterBills
{
    public partial class Central : Form
    {
        public Central()
        {
            InitializeComponent()
        }

        private sub ShowWaterBills()
        {
            . . .
        }

        private sub Central_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        {
            ShowWaterBills()
        }

        private sub BtnCreateWaterBill_Click(sender As Object, e As EventArgs)
        {
            Create create = new()

            create.ShowDialog()

            ShowWaterBills()
        }

        private sub BtnViewWaterBill_Click(sender As Object, e As EventArgs)
        {
            Details details = new()

            details.ShowDialog()
        }
    }
}

To execute the application, on the main menu, click Debug -> Start Without Debugging
On the Water Distribution form, click the Water Bills button:
On the Water Bills form, click the View Water Bill button:
In the Water Bill # text box, type 917829
Click the Find Water Bill button:
Close the Details form
Close the forms and return to your programming environment

Water Bill Edition

Although it doesn't happen regularly, some information can change about an existing water bill. If that happens, the user must be able to update the water bill. For this reason, we will create and provide a form that supports that operation.

Practical Learning: Editing a Water Bill

To create a new form, in the Solution Explorer, right-click Water Bills -> New -> Form (Windows Forms)...
Type Editor as the name of the form
Click Add
Make that form the same size as the Create Water Bill form
Select everything on the Create Water Bill form. Copy that selection and paste it in the new Water Bill Editor form
Copy the Find Water Bill button from the Water Bill Details form and paste it on the Water Bill Editor form

Complete the design of the form as follows:

Control	(Name)	Text	Other Properties
Label		Water Bill #:
TextBox	TxtBillNumber		Modifiers: Public
Button	BtnFindWaterBill	&Find Water Bill
GroupBox		Customer Information
Label		Account #:
MaskedTextBox	MtbAccountNumber		Masked: 0000-000-0000 Modifiers: Public
Button	BtnFindCustomerAccount	Find Customer Account
Label		Account Name:
TextBox	TxtAccountName		Enabled: False
Label		Address:
TextBox	TxtAddress		Enabled: False
TextBox	TxtCity		Enabled: False
TextBox	TxtCounty		Enabled: False
TextBox	TxtState		Enabled: False
TextBox	MtbZIPCode		Enabled: False
Label		______________________________________________
Label		Meter Details:
TextBox	TxtMeterDetails		Modifiers: Public
GroupBox		Meter Reading
Label		Meter Reading Start Date:
DateTimePicker	dtpMeterReadingStartDate		Modifiers: Public
Label		Meter Reading End Date:
DateTimePicker	dtpMeterReadingEndDate		Modifiers: Public
Label		Counter Reading Start:
TextBox	TxtCounterReadingStart		Modifiers: Public
Label		Counter Reading End:
TextBox	TxtCounterReadingEnd		Modifiers: Public
Button	BtnEvaluateWaterBill	Evaluate Water Bill
GroupBox		Meter Result
Label		Billing Days:
TextBox	TxtBillingDays		TextAlign: Right Modifiers: Public
Label		Total Gallons:
TextBox	TxtTotalGallons		TextAlign: Right Modifiers: Public
Label		Total CCF:
TextBox	TxtTotalCCF		TextAlign: Right Modifiers: Public
Label		First Tier Consumption:
TextBox	TxtFirstTierConsumption		TextAlign: Right Modifiers: Public
Label		Second Tier:
TextBox	TxtSecondTierConsumption		TextAlign: Right Modifiers: Public
Label		Last Tier:
TextBox	TxtLastTierConsumption		TextAlign: Right Modifiers: Public
GroupBox		Consumption Charges
Label		Water Charges:
TextBox	TxtWaterCharges		TextAlign: Right Modifiers: Public
Label		Sewer Charges:
TextBox	TxtSewerCharges		TextAlign: Right Modifiers: Public
Label		Environment Charges:
TextBox	TxtEnvironmentCharges		TextAlign: Right Modifiers: Public
Label		Total Charges:
TextBox	TxtTotalCharges		TextAlign: Right Modifiers: Public
GroupBox		Taxes
Label		Local Taxes:
TextBox	TxtLocalTaxes		TextAlign: Right Modifiers: Public
Label		State Taxes:
TextBox	TxtStateTaxes		TextAlign: Right Modifiers: Public
GroupBox		Water Bill Payment
Label		Payment Due Date:
DateTimePicker	dtpPaymentDueDate		Modifiers: Public
Label		Amount Due:
TextBox	TxtAmountDue		TextAlign: Right Modifiers: Public
Label		Late Payment Due Date:
DateTimePicker	dtpLatePaymentDueDate		Modifiers: Public
Label		Late Amount Due:
TextBox	TxtLateAmountDue		TextAlign: Right Modifiers: Public
Button	BtnUpdateWaterBill	Update Water Bill	DialogResult: OK
Button	BtnClose	Close	DialogResult: Cancel

Using the Properties window, change some characteristics of the form as follows:

FormBorderStyle: FixedDialog
Text:            Stellar Water Point - Water Bill Edition
StartPosition:   CenterScreen
MinimizeBox:     False
MaximizeBox:     False
AcceptButton:    BtnUpdateWaterBill
CancelButton:    BtnClose

On the form, double-click the Find Water Bill button

Change the document as follows:

import System.Xmlimport System.Xml
{
    public partial class Editor : Form
    {
        public Editor()
        {
            InitializeComponent()
        }

        private sub BtnFindWaterBill_Click(sender As Object, e As EventArgs)
        {
            if string.IsNullOrEmpty(TxtBillNumber.Text))
            {
                MsgBox("You must provide a water bill number and then click the Find Water Bill button.",
                                "Stellar Water Point", MsgBoxStyle.OkOnly Or MsgBoxStyle.Information)
                Exit Sub
            }

            XmlDocument xdWaterBills = new XmlDocument()
            string? strWaterBills = "C:\Stellar Water Point10\WaterBills.xml"

            FileInfo? fiWaterBills = new FileInfo(strWaterBills)

            if fiWaterBills.Exists)
            {
                using (FileStream? fsWaterBills = new FileStream(fiWaterBills.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterBills.Load(fsWaterBills)

                    XmlNodeList xnlWaterBills = xdWaterBills.DocumentElement!.SelectNodes("//bill-number[.='" + TxtBillNumber.Text + "']")!;

                    foreach (XmlNode xnWaterBill in xnlWaterBills)
                    {
                        TxtBillNumber.Text            =                xnWaterBill.FirstChild.InnerText
                        MtbAccountNumber.Text         =                xnWaterBill.NextSibling.InnerText
                        dtpMeterReadingStartDate.Text = DateTime.Parse(xnWaterBill.NextSibling.NextSibling!.InnerText).ToLongDateString()
                        dtpMeterReadingEndDate.Text   = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling!.InnerText).ToLongDateString()
                        TxtBillingDays.Text           =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling.InnerText
                        TxtCounterReadingStart.Text   =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling.InnerText
                        TxtCounterReadingEnd.Text     =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtTotalHCF.Text              =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtTotalGallons.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtFirstTierConsumption.Text  =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtSecondTierConsumption.Text =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtLastTierConsumption.Text   =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtWaterCharges.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtSewerCharges.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtEnvironmentCharges.Text    =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtServiceCharges.Text        =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtTotalCharges.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtStateTaxes.Text            =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtLocalTaxes.Text            =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        dtpPaymentDueDate.Text        = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText).ToLongDateString()
                        TxtAmountDue.Text             =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        dtpLatePaymentDueDate.Text    = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText).ToLongDateString()
                        TxtLateAmountDue.Text         =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                    }
                }
            }

            XmlDocument xdCustomers = new XmlDocument()
            string? strCustomers = "C:\Stellar Water Point10\Customers.xml"

            FileInfo? fiCustomers = new FileInfo(strCustomers)

            string strMeterNumber = string.Empty;

            if fiCustomers.Exists)
            {
                using  fsCustomers as FileStream= new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdCustomers.Load(fsCustomers)
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + MtbAccountNumber.Text + "']")!;

                    for each xnCustomer as XmlNode  in xnlCustomers
                    {
                        TxtAccountName.Text = xnCustomer.NextSibling.InnerText rem Account Name

                        strMeterNumber = xnCustomer.NextSibling.NextSibling.InnerText   rem Meter Number
                        TxtAccountType.Text = xnCustomer.NextSibling.NextSibling.NextSibling.InnerText   rem Account Type
                        TxtAddress.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.InnerText   rem Address
                        TxtCity.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.InnerText   rem City
                        TxtCounty.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling.InnerText   rem County
                        TxtState.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText   rem State
                        TxtZIPCode.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText rem ZIP-Code
                    }
                }
            }

            dim xdWaterMeters as XmlDocument = new XmlDocument()
            dim strWaterMeters as string= "C:\Stellar Water Point10\WaterMeters.xml"

            dim fiWaterMeters as FileInfo= new FileInfo(strWaterMeters)

            if fiWaterMeters.Exists)
            {
                using  fsWaterMeters as FileStream= new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterMeters.Load(fsWaterMeters)
                    dim xnlWaterMeters  as XmlNodeList = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;

                    rem Check each node of the XML record
                    for each xnWaterMeter  as XmlNode in xnlWaterMeters)
                    {
                        TxtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")"
                    }
                }
            }
        }
    }
}

Return to the Water Bill - Editor form and double-click the Find Customer Account button

Implement the event as follows:

import System.Xml

namespace StellarWaterPoint1.WaterBills
{
    public partial class Editor : Form
    {
        public Editor()
        {
            InitializeComponent()
        }

        private sub BtnFindWaterBill_Click(sender As Object, e As EventArgs)
        {
            . . .
        }

        private sub BtnFindCustomerAccount_Click(sender As Object, e As EventArgs)
        {
            XmlDocument xdCustomers = new XmlDocument()
            string? strCustomers = "C:\Stellar Water Point10\Customers.xml"

            FileInfo? fiCustomers = new FileInfo(strCustomers)

            string strMeterNumber = string.Empty;

            if fiCustomers.Exists)
            {
                using  fsCustomers as FileStream= new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdCustomers.Load(fsCustomers)
                    XmlNodeList xnlCustomers   = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + MtbAccountNumber.Text + "']")!;

                    for each xnCustomer as XmlNode  in xnlCustomers
                    {
                        TxtAccountName.Text    = xnCustomer.NextSibling.InnerText
                        strMeterNumber         = xnCustomer.NextSibling.NextSibling.InnerText
                        TxtAccountType.Text    = xnCustomer.NextSibling.NextSibling.NextSibling.InnerText
                        TxtAddress.Text        = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.InnerText
                        TxtCity.Text           = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.InnerText
                        TxtCounty.Text         = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtState.Text          = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtZIPCode.Text        = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                    }
                }
            }

            dim xdWaterMeters as XmlDocument = new XmlDocument()
            dim strWaterMeters as string= "C:\Stellar Water Point10\WaterMeters.xml"

            dim fiWaterMeters as FileInfo= new FileInfo(strWaterMeters)

            if fiWaterMeters.Exists)
            {
                using  fsWaterMeters as FileStream= new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterMeters.Load(fsWaterMeters)
                    dim xnlWaterMeters  as XmlNodeList = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;

                    for each xnWaterMeter  as XmlNode in xnlWaterMeters)
                    {
                        TxtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")"
                    }
                }
            }
        }
    }
}

Return to the Water Bill - Editor form and double-click the Meter Reading End Date date time picker

Implement the event as follows:

import System.Xml

namespace StellarWaterPoint1.WaterBills
{
    public partial class Editor : Form
    {
        public Editor()
        {
            InitializeComponent()
        }

        private sub BtnFindWaterBill_Click(sender As Object, e As EventArgs)
        {
            . . .
        }

        private sub BtnFindCustomerAccount_Click(sender As Object, e As EventArgs)
        {
            . . .
        }

        private sub dtpMeterReadingEndDate_ValueChanged(sender As Object, e As EventArgs)
        {
            TimeSpan tsDays = dtpMeterReadingEndDate.Value - dtpMeterReadingStartDate.Value;

            TxtBillingDays.Text = (tsDays.Days + 1).ToString()
        }
    }
}

Return to the Water Bill - Editor form and double-click the Re-Evaluate Water Bill button

Implement the event as follows:

import System.Xml

namespace StellarWaterPoint1.WaterBills
{
    public partial class Editor : Form
    {
        public Editor()
        {
            InitializeComponent()
        }

        private sub BtnFindWaterBill_Click(sender As Object, e As EventArgs)
        {
            if string.IsNullOrEmpty(TxtBillNumber.Text))
            {
                MsgBox("You must provide a water bill number and then click the Find Water Bill button.",
                                "Stellar Water Point", MsgBoxStyle.OkOnly Or MsgBoxStyle.Information)
                Exit Sub
            }

            XmlDocument xdWaterBills = new XmlDocument()
            string? strWaterBills = "C:\Stellar Water Point10\WaterBills.xml"

            FileInfo? fiWaterBills = new FileInfo(strWaterBills)

            if fiWaterBills.Exists)
            {
                using (FileStream? fsWaterBills = new FileStream(fiWaterBills.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterBills.Load(fsWaterBills)

                    XmlNodeList xnlWaterBills = xdWaterBills.DocumentElement!.SelectNodes("//bill-number[.='" + TxtBillNumber.Text + "']")!;

                    foreach (XmlNode xnWaterBill in xnlWaterBills)
                    {
                        TxtBillNumber.Text            =                xnWaterBill.FirstChild.InnerText
                        MtbAccountNumber.Text         =                xnWaterBill.NextSibling.InnerText
                        dtpMeterReadingStartDate.Text = DateTime.Parse(xnWaterBill.NextSibling.NextSibling!.InnerText).ToLongDateString()
                        dtpMeterReadingEndDate.Text   = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling!.InnerText).ToLongDateString()
                        TxtBillingDays.Text           =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling.InnerText
                        TxtCounterReadingStart.Text   =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling.InnerText
                        TxtCounterReadingEnd.Text     =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtTotalHCF.Text              =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtTotalGallons.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtFirstTierConsumption.Text  =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtSecondTierConsumption.Text =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtLastTierConsumption.Text   =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtWaterCharges.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtSewerCharges.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtEnvironmentCharges.Text    =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtServiceCharges.Text        =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtTotalCharges.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtStateTaxes.Text            =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtLocalTaxes.Text            =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        dtpPaymentDueDate.Text        = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText).ToLongDateString()
                        TxtAmountDue.Text             =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        dtpLatePaymentDueDate.Text    = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText).ToLongDateString()
                        TxtLateAmountDue.Text         =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                    }
                }
            }

            XmlDocument xdCustomers = new XmlDocument()
            string? strCustomers = "C:\Stellar Water Point10\Customers.xml"

            FileInfo? fiCustomers = new FileInfo(strCustomers)

            string strMeterNumber = string.Empty;

            if fiCustomers.Exists)
            {
                using  fsCustomers as FileStream= new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdCustomers.Load(fsCustomers)
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + MtbAccountNumber.Text + "']")!;

                    for each xnCustomer as XmlNode  in xnlCustomers
                    {
                        TxtAccountName.Text = xnCustomer.NextSibling.InnerText rem Account Name

                        strMeterNumber = xnCustomer.NextSibling.NextSibling.InnerText   rem Meter Number
                        TxtAccountType.Text = xnCustomer.NextSibling.NextSibling.NextSibling.InnerText   rem Account Type
                        TxtAddress.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.InnerText   rem Address
                        TxtCity.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.InnerText   rem City
                        TxtCounty.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling.InnerText   rem County
                        TxtState.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText   rem State
                        TxtZIPCode.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText rem ZIP-Code
                    }
                }
            }

            dim xdWaterMeters as XmlDocument = new XmlDocument()
            dim strWaterMeters as string= "C:\Stellar Water Point10\WaterMeters.xml"

            dim fiWaterMeters as FileInfo= new FileInfo(strWaterMeters)

            if fiWaterMeters.Exists)
            {
                using  fsWaterMeters as FileStream= new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterMeters.Load(fsWaterMeters)
                    dim xnlWaterMeters  as XmlNodeList = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;

                    rem Check each node of the XML record
                    for each xnWaterMeter  as XmlNode in xnlWaterMeters)
                    {
                        TxtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")"
                    }
                }
            }
        }

        private sub BtnFindCustomerAccount_Click(sender As Object, e As EventArgs)
        {
            XmlDocument xdCustomers = new XmlDocument()
            string? strCustomers = "C:\Stellar Water Point10\Customers.xml"

            FileInfo? fiCustomers = new FileInfo(strCustomers)

            string strMeterNumber = string.Empty;

            if fiCustomers.Exists)
            {
                using  fsCustomers as FileStream= new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdCustomers.Load(fsCustomers)
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + MtbAccountNumber.Text + "']")!;

                    for each xnCustomer as XmlNode  in xnlCustomers
                    {
                        TxtAccountName.Text = xnCustomer.NextSibling.InnerText
                        strMeterNumber = xnCustomer.NextSibling.NextSibling.InnerText
                        TxtAccountType.Text = xnCustomer.NextSibling.NextSibling.NextSibling.InnerText
                        TxtAddress.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.InnerText
                        TxtCity.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.InnerText
                        TxtCounty.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtState.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtZIPCode.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                    }
                }
            }

            dim xdWaterMeters as XmlDocument = new XmlDocument()
            dim strWaterMeters as string= "C:\Stellar Water Point10\WaterMeters.xml"

            dim fiWaterMeters as FileInfo= new FileInfo(strWaterMeters)

            if fiWaterMeters.Exists)
            {
                using  fsWaterMeters as FileStream= new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterMeters.Load(fsWaterMeters)
                    dim xnlWaterMeters  as XmlNodeList = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;

                    for each xnWaterMeter  as XmlNode in xnlWaterMeters)
                    {
                        TxtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")"
                    }
                }
            }
        }

        private sub dtpMeterReadingEndDate_ValueChanged(sender As Object, e As EventArgs)
        {
            TimeSpan tsDays = dtpMeterReadingEndDate.Value - dtpMeterReadingStartDate.Value;

            TxtBillingDays.Text = (tsDays.Days + 1).ToString()
        }

        (double a, double b, double c) CalculateTiers(string acnt, double total)
        {
            (double tier1, double tier2, double tier3) results = (0.00, 0.00, 0.00)

            if acnt="RES")
            {
                results.tier1 = total * 41.50 / 10000.00;
                results.tier2 = total * 32.50 / 10000.00;
                results.tier3 = total * 26.00 / 10000.00;
            }
            else if acnt="SGO")
            {
                results.tier1 = total * 46 / 10000;
                results.tier2 = total * 50 / 10000;
                results.tier3 = total *  4 / 10000;
            }
            else if acnt="BUS")
            {
                results.tier1 = total * 45 / 10000;
                results.tier2 = total * 30 / 10000;
                results.tier3 = total * 25 / 10000;
            }
            else if acnt="UUO")
            {
                results.tier1 = total * 25 / 10000;
                results.tier2 = total * 35 / 10000;
                results.tier3 = total * 40 / 10000;
            }
            else if acnt="WAT")
            {
                results.tier1 = total * 50 / 10000;
                results.tier2 = total * 40 / 10000;
                results.tier3 = total * 10 / 10000;
            }
            else if acnt="OTH")
            {
                results.tier1 = total * (48.00 / 10000.00)
                results.tier2 = total * (32.00 / 10000.00)
                results.tier3 = total * (20.00 / 10000.00)
            }

            return results;
        }

        private double CalculateSewerCharges(string acnt, double total)
        {
            double result;

            if acnt="RES")
            {
                result = total * 6.826941 / 100;
            }
            else if acnt="SGO")
            {
                result = total * 4.162522 / 100;
            }
            else if acnt="BUS")
            {
                result = total * 8.3136 / 100;
            }
            else if acnt="UUO")
            {
                result = total * 10.6247 / 100;
            }
            else if acnt="WAT")
            {
                result = total * 12.0535 / 100;
            }
            else rem OTH
            {
                result = total * 9.2065 / 100;
            }

            return result;
        }

        private double CalculateEnvironmentCharges(string acnt, double total)
        {
            double result;

            switch (acnt)
            {
                case "RES":
                    result = total * 0.022724;
                    Exit For
                case "SGO":
                    result = total * 0.118242;
                    Exit For
                case "BUS":
                    result = total * 0.161369;
                    Exit For
                case "UUO":
                    result = total * 0.082477;
                    Exit For
                case "WAT":
                    result = total * 0.413574;
                    Exit For
                default:
                    result = total * 0.22184;
                    Exit For
            }

            return result;
        }

        private double CalculateServiceCharges(string acnt, double total)
        {
            if acnt="RES")
            {
                return total * 0.145748;
            }
            else if acnt="SGO")
            {
                return total * 0.10224;
            }
            else if acnt="BUS")
            {
                return total * 0.242627;
            }
            else if acnt="UUO")
            {
                return total * 0.18669;
            }
            else if acnt="WAT")
            {
                return total * 0.412628;
            }
            else
            {
                return total * 0.210248;
            }
        }

        private double CalculateLocalTaxes(string acnt, double total) => acnt switch
        {
            "RES" => total * 0.031574,
            "SGO" => total * 0.035026,
            "BUS" => total * 0.122517,
            "UUO" => total * 0.105737,
            "WAT" => total * 0.153248,
            _ => total * 0.125148
        };

        private double CalculateStateTaxes(string acnt, double total) => acnt switch
        {
            "RES" => total * 0.016724,
            "SGO" => total * 0.008779,
            "BUS" => total * 0.042448,
            "UUO" => total * 0.067958,
            "WAT" => total * 0.081622,
            _ => total * 0.013746
        };

        private DateTime SetPaymentDueDate(string acnt, DateTime date)
        {
            TimeSpan tsPaymentDueDate = new TimeSpan(1, 0, 0, 0)

            if acnt="RES")
            {
                tsPaymentDueDate = new TimeSpan(15, 0, 0, 0)
            }
            else if acnt="SGO")
            {
                tsPaymentDueDate = new TimeSpan(20, 0, 0, 0)
            }
            else if acnt="BUS")
            {
                tsPaymentDueDate = new TimeSpan(30, 0, 0, 0)
            }
            else if acnt="UUO")
            {
                tsPaymentDueDate = new TimeSpan(15, 0, 0, 0)
            }
            else if acnt="WAT")
            {
                tsPaymentDueDate = new TimeSpan(40, 0, 0, 0)
            }
            else
            {
                tsPaymentDueDate = new TimeSpan(35, 0, 0, 0)
            }

            return date + tsPaymentDueDate;
        }

        private DateTime SetLatePaymentDueDate(string acnt, DateTime date)
        {
            TimeSpan tsLatePaymentDueDate = new TimeSpan(1, 0, 0, 0)

            if acnt="RES")
            {
                tsLatePaymentDueDate = new TimeSpan(30, 0, 0, 0)

                return date + tsLatePaymentDueDate;
            }
            else if acnt="SGO")
            {
                tsLatePaymentDueDate = new TimeSpan(40, 0, 0, 0)

                return date + tsLatePaymentDueDate;
            }
            else if acnt="BUS")
            {
                tsLatePaymentDueDate = new TimeSpan(50, 0, 0, 0)

                return date + tsLatePaymentDueDate;
            }
            else if acnt="UUO")
            {
                tsLatePaymentDueDate = new TimeSpan(60, 0, 0, 0)

                return date + tsLatePaymentDueDate;
            }
            else if acnt="WAT")
            {
                tsLatePaymentDueDate = new TimeSpan(65, 0, 0, 0)

                return date + tsLatePaymentDueDate;
            }
            else
            {
                tsLatePaymentDueDate = new TimeSpan(45, 0, 0, 0)

                return date + tsLatePaymentDueDate;
            }
        }

        private double CalculateLateAmountDue(string acnt, double amt)
        {
            double result;

            if acnt="RES")
            {
                result = amt + 8.95;
            }
            else if acnt="SGO")
            {
                result = amt + (amt / 4.575)
            }
            else if acnt="BUS")
            {
                result = amt + (amt / 12.315)
            }
            else if acnt="UUO")
            {
                result = amt + (amt / 7.425)
            }
            else if acnt="WAT")
            {
                result = amt + (amt / 15.225)
            }
            else
            {
                result = amt + (amt / 6.735)
            }

            return result;
        }

        private sub BtnEvaluateWaterBill_Click(sender As Object, e As EventArgs)
        {
            double counterStart = 0, counterEnd = 0;

            try
            {
                counterStart = double.Parse(TxtCounterReadingStart.Text)
            }
            catch (FormatException feCRStart)
            {
                MsgBox("There was a problem with the value of the " +
                                "Counter Reading Start. The error produced is: " + feCRStart.Message,
                                "Stellar Water Point", MsgBoxStyle.OkOnly Or MsgBoxStyle.Information)
            }

            try
            {
                counterEnd = double.Parse(TxtCounterReadingEnd.Text)
            }
            catch (FormatException feCREnd)
            {
                MsgBox("There was a problem with the value of the " +
                                "Counter Reading End. The error produced is: " + feCREnd.Message,
                                "Stellar Water Point", MsgBoxStyle.OkOnly Or MsgBoxStyle.Information)
            }

            double consumption = counterEnd - counterStart;
            double gallons = consumption * 748.05;

            string strAccountType = TxtAccountType.Text[..3];

            (double first, double second, double last) tiers = CalculateTiers(strAccountType, gallons)

            double waterCharges = tiers.first + tiers.second + tiers.last;
            double sewerCharges = CalculateSewerCharges(strAccountType, waterCharges)
            double envCharges = CalculateEnvironmentCharges(strAccountType, waterCharges)
            double srvCharges = CalculateServiceCharges(strAccountType, waterCharges)
            double totalCharges = waterCharges + sewerCharges + envCharges + srvCharges;
            double localTaxes = CalculateLocalTaxes(strAccountType, waterCharges)
            double stateTaxes = CalculateStateTaxes(strAccountType, waterCharges)
            double amtDue = totalCharges + localTaxes + stateTaxes;

            TxtTotalHCF.Text = consumption.ToString()
            TxtTotalGallons.Text = gallons.ToString("F")
            TxtFirstTierConsumption.Text = tiers.first.ToString("F")
            TxtSecondTierConsumption.Text = tiers.second.ToString("F")
            TxtLastTierConsumption.Text = tiers.last.ToString("F")
            TxtWaterCharges.Text = waterCharges.ToString("F")
            TxtSewerCharges.Text = sewerCharges.ToString("F")
            TxtEnvironmentCharges.Text = envCharges.ToString("F")
            TxtServiceCharges.Text = srvCharges.ToString("F")
            TxtTotalCharges.Text = totalCharges.ToString("F")
            TxtLocalTaxes.Text = localTaxes.ToString("F")
            TxtStateTaxes.Text = stateTaxes.ToString("F")
            dtpPaymentDueDate.Value = SetPaymentDueDate(strAccountType, dtpMeterReadingEndDate.Value)
            TxtAmountDue.Text = amtDue.ToString("F")
            dtpLatePaymentDueDate.Value = SetLatePaymentDueDate(strAccountType, dtpMeterReadingEndDate.Value)
            TxtLateAmountDue.Text = CalculateLateAmountDue(strAccountType, amtDue).ToString("F")
        }
    }
}

In the Solution Explorer, below the WaterBills folder, double-click Central.cs
From the Toolbox, add a button to the form below the list view and on the right side of the View Water Bill button

Change the characteristics of the button as follows:

Control	(Name)	Text	Other Properties
ListView	LvwWaterBills		No Change
Button	BtnNewWaterBill		No Change
Button	BtnViewWaterBill		No Change
Button	BtnEditWaterBill	&Edit Water Bill...	Anchor: Bottom, Right

Double-click the Edit Water Bill button

Implement the event as follows:

import System.Xml

namespace StellarWaterPoint1.WaterBills
{
    public partial class Central : Form
    {
        public Central()
        {
            InitializeComponent()
        }

        private sub ShowWaterBills()
        {
            . . .
        }

        private sub Central_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        {
            ShowWaterBills()
        }

        private sub BtnCreateWaterBill_Click(sender As Object, e As EventArgs)
        {
            Create create = new()

            create.ShowDialog()

            ShowWaterBills()
        }

        private sub BtnViewWaterBill_Click(sender As Object, e As EventArgs)
        {
            Details details = new()

            details.ShowDialog()
        }

        private sub BtnEditWaterBill_Click(sender As Object, e As EventArgs)
        {
            Editor editor = new()

            if editor.ShowDialog() =MsgBoxResult.OK)
            {
                if string.IsNullOrEmpty(editor.TxtBillNumber.Text))
                {
                    MsgBox("You must first type a bill number and then click the Find Water Bill button. " +
                                    "You can then optionally change some values on the water bill and save it.",
                                    "Stellar Water Point", MessageBoxButtons.OK)
                    Exit Sub
                }

                XmlDocument xdWaterBills = new XmlDocument()
                string? strWaterBills    = "C:\Stellar Water Point10\WaterBills.xml"

                xdWaterBills.Load(strWaterBills)

                XmlNodeList xnlWaterBills = xdWaterBills.DocumentElement!.GetElementsByTagName("bill-number")

                foreach (XmlNode xnWaterBill in xnlWaterBills)
                {
                    if xnWaterBill.InnerText.Contains(editor.TxtBillNumber.Text))
                    {
                        xnWaterBill.ParentNode!.InnerXml =
                            "<bill-number>"              + editor.TxtBillNumber.Text + "</bill-number>" +
                            "<account-number>"           + editor.MtbAccountNumber.Text + "</account-number>" +
                            "<meter-reading-start-date>" + editor.dtpMeterReadingStartDate.Value.ToShortDateString() + "</meter-reading-start-date>" +
                            "<meter-reading-end-date>"   + editor.dtpMeterReadingEndDate.Value.ToShortDateString() + "</meter-reading-end-date>" +
                            "<billing-days>"             + editor.TxtBillingDays.Text + "</billing-days>" +
                            "<counter-reading-start>"    + editor.TxtCounterReadingStart.Text + "</counter-reading-start>" +
                            "<counter-reading-end>"      + editor.TxtCounterReadingEnd.Text + "</counter-reading-end>" +
                            "<total-hcf>"                + editor.TxtTotalHCF.Text + "</total-hcf>" +
                            "<total-gallons>"            + editor.TxtTotalGallons.Text + "</total-gallons>" +
                            "<first-tier-consumption>"   + editor.TxtFirstTierConsumption.Text + "</first-tier-consumption>" +
                            "<second-tier-consumption>"  + editor.TxtSecondTierConsumption.Text + "</second-tier-consumption>" +
                            "<last-tier-consumption>"    + editor.TxtLastTierConsumption.Text + "</last-tier-consumption>" +
                            "<water-charges>"            + editor.TxtWaterCharges.Text + "</water-charges>" +
                            "<sewer-charges>"            + editor.TxtSewerCharges.Text + "</sewer-charges>" +
                            "<environment-charges>"      + editor.TxtEnvironmentCharges.Text + "</environment-charges>" +
                            "<service-charges>"          + editor.TxtEnvironmentCharges.Text + "</service-charges>" +
                            "<total-charges>"            + editor.TxtTotalCharges.Text + "</total-charges>" +
                            "<state-taxes>"              + editor.TxtStateTaxes.Text + "</state-taxes>" +
                            "<local-taxes>"              + editor.TxtLocalTaxes.Text + "</local-taxes>" +
                            "<payment-due-date>"         + editor.dtpPaymentDueDate.Value.ToShortDateString() + "</payment-due-date>" +
                            "<amount-due>"               + editor.TxtAmountDue.Text + "</amount-due>" +
                            "<late-payment-due-date>"    + editor.dtpLatePaymentDueDate.Value.ToShortDateString() + "</late-payment-due-date>" +
                            "<late-amount-due>"          + editor.TxtLateAmountDue.Text + "</late-amount-due>"

                        xdWaterBills.Save(strWaterBills)
                        Exit For
                    }
                }
            }
            
            ShowWaterBills()
        }
    }
}

To execute the application, on the main menu, click Debug -> Start Without Debugging
On the main form of the application, click the Customers button:
Click the Edit Water Bill button:
In the Water Bill # text, type 923633
Click the Find Water Bill button

Change the following values:

Account #:                9249-379-6848 and click Find Customer Account
Meter Reading Start Date: 1/19/2010
Meter Reading End Date:   4/17/2010
Counter Reading Start:    256953
Counter Reading End:      256966

Click the Re-Evaluate Water Bill button:
Click the Update Water Bill button:
Close the forms and return to your programming environment

Deleting a Water Bill

If something is completely wrong about a water bill so much that such a water bill must be removed from the application, the water bill must be deleted. To assist the user with such an operation, we will create the necessary form.

Practical Learning: Deleting a Customer Account

To create a new form, in the Solution Explorer, right-click Water Bills -> New -> Form (Windows Forms)...
Set the name of the file and form to Delete
Click Add
Make that form the same size as the Water Bill - Details form
Select everything on the Water Bill - Details form and copy that selection
Paste that selection in the Water Bill - Delete form

Complete the design of the form as follows:

Control		(Name)	Text
Button		BtnDeleteWaterBill	&Delete Water Bill

Using the Properties window, change some characteristics of the form as follows:

FormBorderStyle: FixedDialog
Text:            Stellar Water Point - Water Bill Deletion
StartPosition:   CenterScreen
MinimizeBox:     False
MaximizeBox:     False
ShowInTaskbar:   False

On the form, double-click the Find Water Bill button

Change the document as follows:

import System.Xml

namespace StellarWaterPoint1.WaterBills
{
    public partial class Delete : Form
    {
        public Delete()
        {
            InitializeComponent()
        }

        private sub BtnFindWaterBill_Click(sender As Object, e As EventArgs)
        {
            rem If the user clicks the Find Water Meter button, 
             * make sure there is an invoice number in the top text box.
            if string.IsNullOrEmpty(TxtBillNumber.Text))
            {
                MsgBox("You must provide a water bill number and then click the Find Water Bill button.",
                                "Stellar Water Point", MsgBoxStyle.OkOnly Or MsgBoxStyle.Information)
                rem If the user didn't type a bill number but clicked Find Water Bill, don't do anything
                Exit Sub
            }

            XmlDocument xdWaterBills = new XmlDocument()
            string? strWaterBills = "C:\Stellar Water Point10\WaterBills.xml"

            FileInfo? fiWaterBills = new FileInfo(strWaterBills)

            if fiWaterBills.Exists)
            {
                using (FileStream? fsWaterBills = new FileStream(fiWaterBills.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterBills.Load(fsWaterBills)

                    rem Use XPath to locate the water bill that has 
                     * the same invoice number as the one in the Water Bill Number text box.
                     * Store the water bill in an XmlNodeList variable.
                    XmlNodeList xnlWaterBills = xdWaterBills.DocumentElement!.SelectNodes("//bill-number[.='" + TxtBillNumber.Text + "']")!;

                    foreach (XmlNode xnWaterBill in xnlWaterBills)
                    {
                        TxtBillNumber.Text            =                xnWaterBill.FirstChild.InnerText
                        TxtAccountNumber.Text         =                xnWaterBill.NextSibling.InnerText
                        TxtMeterReadingStartDate.Text = DateTime.Parse(xnWaterBill.NextSibling.NextSibling!.InnerText).ToLongDateString()
                        TxtMeterReadingEndDate.Text   = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling!.InnerText).ToLongDateString()
                        TxtBillingDays.Text           =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling.InnerText
                        TxtCounterReadingStart.Text   =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling.InnerText
                        TxtCounterReadingEnd.Text     =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtTotalHCF.Text              =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtTotalGallons.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtFirstTierConsumption.Text  =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtSecondTierConsumption.Text =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtLastTierConsumption.Text   =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtWaterCharges.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtSewerCharges.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtEnvironmentCharges.Text    =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtServiceCharges.Text        =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtTotalCharges.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtStateTaxes.Text            =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtLocalTaxes.Text            =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtPaymentDueDate.Text        = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText).ToLongDateString()
                        TxtAmountDue.Text             =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtLatePaymentDueDate.Text    = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText).ToLongDateString()
                        TxtLateAmountDue.Text         =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                    }
                }
            }

            XmlDocument xdCustomers = new XmlDocument()
            rem Declare a variable for a file that holds the list of customers
            string? strCustomers = "C:\Stellar Water Point10\Customers.xml"

            rem Create a FileInfo object for the customers
            FileInfo? fiCustomers = new FileInfo(strCustomers)

            rem We will need to know the water meter associated with this customer account
            string strMeterNumber = string.Empty;

            rem Check whether the file that holds a list of customers exists
            if fiCustomers.Exists)
            {
                rem If that exists, open it and pass it to a FileStream object
                using  fsCustomers as FileStream= new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    rem Get the list of customers and pass the records to the XML DOM object created earlier
                    xdCustomers.Load(fsCustomers)
                    rem Create an XmlNodeList list of customers using XPath
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + TxtAccountNumber.Text + "']")!;

                    rem Check each node of the XML record and display its values in each Windows control on the form
                    for each xnCustomer as XmlNode  in xnlCustomers
                    {
                        //MtbAccountNumber.Text = xnCustomer.NextSibling.InnerText   rem Meter #
                        TxtAccountName.Text = xnCustomer.NextSibling.InnerText rem Account Name

                        strMeterNumber = xnCustomer.NextSibling.NextSibling.InnerText   rem Meter Number
                        TxtAccountType.Text = xnCustomer.NextSibling.NextSibling.NextSibling.InnerText   rem Account Type
                        TxtAddress.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.InnerText   rem Address
                        TxtCity.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.InnerText   rem City
                        TxtCounty.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling.InnerText   rem County
                        TxtState.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText   rem State
                        TxtZIPCode.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText rem ZIP-Code
                    }
                }
            }

            rem Create an XML DOM object for the water meters records
            dim xdWaterMeters as XmlDocument = new XmlDocument()
            rem Declare a variable for a file that holds the list of water meters
            dim strWaterMeters as string= "C:\Stellar Water Point10\WaterMeters.xml"

            rem Create a FileInfo object for the customers
            dim fiWaterMeters as FileInfo= new FileInfo(strWaterMeters)

            rem Check whether the file that holds a list of water meters exists
            if fiWaterMeters.Exists)
            {
                rem Get the list of water meters and pass the records to the XML DOM object
                using  fsWaterMeters as FileStream= new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    rem Get the list of water meters and pass the records to the XML DOM object
                    xdWaterMeters.Load(fsWaterMeters)
                    rem Create an XmlNodeList list of water meters using XPath
                    dim xnlWaterMeters  as XmlNodeList = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;

                    rem Check each node of the XML record
                    for each xnWaterMeter  as XmlNode in xnlWaterMeters)
                    {
                        rem Get the values for the water meter.
                         * Create a sentence and display it in the Meter Details text box.
                        TxtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")"
                    }
                }
            }
        }
    }
}

Return to the Water Bills - Delete form and double-click the Delete Water Bill button
Return to the form and double-click the Close button

Change the document as follows:

import System.Xml

namespace StellarWaterPoint1.WaterBills
{
    public partial class Delete : Form
    {
        public Delete()
        {
            InitializeComponent()
        }

        private sub BtnFindWaterBill_Click(sender As Object, e As EventArgs)
        {
            rem If the user clicks the Find Water Meter button, 
             * make sure there is an invoice number in the top text box.
            if string.IsNullOrEmpty(TxtBillNumber.Text))
            {
                MsgBox("You must provide a water bill number and then click the Find Water Bill button.",
                                "Stellar Water Point", MsgBoxStyle.OkOnly Or MsgBoxStyle.Information)
                rem If the user didn't type a bill number but clicked Find Water Bill, don't do anything
                Exit Sub
            }

            XmlDocument xdWaterBills = new XmlDocument()
            string? strWaterBills = "C:\Stellar Water Point10\WaterBills.xml"

            FileInfo? fiWaterBills = new FileInfo(strWaterBills)

            if fiWaterBills.Exists)
            {
                using (FileStream? fsWaterBills = new FileStream(fiWaterBills.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterBills.Load(fsWaterBills)

                    rem Use XPath to locate the water bill that has 
                     * the same invoice number as the one in the Water Bill Number text box.
                     * Store the water bill in an XmlNodeList variable.
                    XmlNodeList xnlWaterBills = xdWaterBills.DocumentElement!.SelectNodes("//bill-number[.='" + TxtBillNumber.Text + "']")!;

                    foreach (XmlNode xnWaterBill in xnlWaterBills)
                    {
                        TxtBillNumber.Text            =                xnWaterBill.FirstChild.InnerText
                        TxtAccountNumber.Text         =                xnWaterBill.NextSibling.InnerText
                        TxtMeterReadingStartDate.Text = DateTime.Parse(xnWaterBill.NextSibling.NextSibling!.InnerText).ToLongDateString()
                        TxtMeterReadingEndDate.Text   = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling!.InnerText).ToLongDateString()
                        TxtBillingDays.Text           =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling.InnerText
                        TxtCounterReadingStart.Text   =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling.InnerText
                        TxtCounterReadingEnd.Text     =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtTotalHCF.Text              =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtTotalGallons.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtFirstTierConsumption.Text  =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtSecondTierConsumption.Text =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtLastTierConsumption.Text   =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtWaterCharges.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtSewerCharges.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtEnvironmentCharges.Text    =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtServiceCharges.Text        =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtTotalCharges.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtStateTaxes.Text            =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtLocalTaxes.Text            =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtPaymentDueDate.Text        = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText).ToLongDateString()
                        TxtAmountDue.Text             =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                        TxtLatePaymentDueDate.Text    = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText).ToLongDateString()
                        TxtLateAmountDue.Text         =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText
                    }
                }
            }

            XmlDocument xdCustomers = new XmlDocument()
            rem Declare a variable for a file that holds the list of customers
            string? strCustomers = "C:\Stellar Water Point10\Customers.xml"

            rem Create a FileInfo object for the customers
            FileInfo? fiCustomers = new FileInfo(strCustomers)

            rem We will need to know the water meter associated with this customer account
            string strMeterNumber = string.Empty;

            rem Check whether the file that holds a list of customers exists
            if fiCustomers.Exists)
            {
                rem If that exists, open it and pass it to a FileStream object
                using  fsCustomers as FileStream= new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    rem Get the list of customers and pass the records to the XML DOM object created earlier
                    xdCustomers.Load(fsCustomers)
                    rem Create an XmlNodeList list of customers using XPath
                    XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + TxtAccountNumber.Text + "']")!;

                    rem Check each node of the XML record and display its values in each Windows control on the form
                    for each xnCustomer as XmlNode  in xnlCustomers
                    {
                        //MtbAccountNumber.Text = xnCustomer.NextSibling.InnerText   rem Meter #
                        TxtAccountName.Text = xnCustomer.NextSibling.InnerText rem Account Name

                        strMeterNumber = xnCustomer.NextSibling.NextSibling.InnerText   rem Meter Number
                        TxtAccountType.Text = xnCustomer.NextSibling.NextSibling.NextSibling.InnerText   rem Account Type
                        TxtAddress.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.InnerText   rem Address
                        TxtCity.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.InnerText   rem City
                        TxtCounty.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling.InnerText   rem County
                        TxtState.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText   rem State
                        TxtZIPCode.Text = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling.InnerText rem ZIP-Code
                    }
                }
            }

            rem Create an XML DOM object for the water meters records
            dim xdWaterMeters as XmlDocument = new XmlDocument()
            rem Declare a variable for a file that holds the list of water meters
            dim strWaterMeters as string= "C:\Stellar Water Point10\WaterMeters.xml"

            rem Create a FileInfo object for the customers
            dim fiWaterMeters as FileInfo= new FileInfo(strWaterMeters)

            rem Check whether the file that holds a list of water meters exists
            if fiWaterMeters.Exists)
            {
                rem Get the list of water meters and pass the records to the XML DOM object
                using  fsWaterMeters as FileStream= new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    rem Get the list of water meters and pass the records to the XML DOM object
                    xdWaterMeters.Load(fsWaterMeters)
                    rem Create an XmlNodeList list of water meters using XPath
                    dim xnlWaterMeters  as XmlNodeList = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;

                    rem Check each node of the XML record
                    for each xnWaterMeter  as XmlNode in xnlWaterMeters)
                    {
                        rem Get the values for the water meter.
                         * Create a sentence and display it in the Meter Details text box.
                        TxtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                               xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                               xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")"
                    }
                }
            }
        }

        private sub BtnDeleteWaterBill_Click(sender As Object, e As EventArgs)
        {
            dim xdWaterMeters as XmlDocument = new XmlDocument()
            dim strWaterMeters as string= "C:\Stellar Water Point10\WaterBills.xml"

            if string.IsNullOrEmpty(TxtBillNumber.Text))
            {
                MsgBox("You must provide a bill number for the water bill you want to delete.",
                                "Stellar Water Point", MsgBoxStyle.OkOnly Or MsgBoxStyle.Information)
                Exit Sub
            }

            if !File.Exists(strWaterMeters))
            {
                MsgBox("There is no file for the water bills in the system.",
                                "Stellar Water Point",
                                MsgBoxStyle.OkOnly Or MsgBoxStyle.Information)
                Exit Sub
            }

            xdWaterMeters.Load(strWaterMeters)

            dim xnlWaterMeters  as XmlNodeList = xdWaterMeters.DocumentElement!.GetElementsByTagName("bill-number")

            for each xnWaterMeter  as XmlNode in xnlWaterMeters)
            {
                if xnWaterMeter.InnerText=TxtBillNumber.Text)
                {
                    if MsgBox("Are you sure you want to delete this water bill from the system?",
                                        "Stellar Water Point",
                                        MessageBoxButtons.YesNo, MessageBoxIcon.Question) =MsgBoxResult.Yes)
                    {
                        xdWaterMeters.DocumentElement.RemoveChild(xnWaterMeter.ParentNode!)
                        Exit For
                    }
                }
            }

            xdWaterMeters.Save(strWaterMeters)

            Close()
        }

        private sub BtnClose_Click(sender As Object, e As EventArgs)
        {
            Close()
        }
    }
}

In the Solution Explorer, below the WaterBills folder, double-click Central.cs to open its form
From the Toolbox, add two buttons to the form below the list view and to the right of the Edit Water Bill button

Change the form design as follows:

Control	(Name)	Text	Other Properties
ListView	LvwWaterBills		Anchor: Bottom, Top, Bottom, Left, Right
Button	BtnCreateWaterBill	&Create Water Bill...	Anchor: Bottom, Right
Button	BtnViewWaterBill	&View Water Bill...	Anchor: Bottom, Right
Button	BtnEditWaterBill	&Edit Water Bill...	Anchor: Bottom, Right
Button	BtnDeleteWaterBill	&Delete Water Bill...	Anchor: Bottom, Right
Button	BtnClose	&Close	Anchor: Bottom, Right

On the form, double-click the Delete Water Bill button
Return to the Water Bills - Central form and double-click the Close button

Implement the events as follows:

import System.Xml

namespace StellarWaterPoint1.WaterBills
{
    public partial class Central : Form
    {
        public Central()
        {
            InitializeComponent()
        }

        private sub ShowWaterBills()
        {
            lvwWaterBills.Items.Clear()

            XmlDocument xdWaterBills = new XmlDocument()
            string? strWaterBills = "C:\Stellar Water Point10\WaterBills.xml"

            FileInfo? fiWaterBills = new FileInfo(strWaterBills)

            if fiWaterBills.Exists)
            {
                using (FileStream? fsWaterBills = new FileStream(fiWaterBills.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    xdWaterBills.Load(fsWaterBills)
                    XmlNodeList xnlWaterBills = xdWaterBills.DocumentElement!.ChildNodes;

                    int i = 1;

                    foreach (XmlNode xnWaterBill in xnlWaterBills)
                    {
                        ListViewItem lviWaterBill = new ListViewItem(i.ToString())

                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild!.InnerText)   rem Water Bill #
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling!.InnerText)   rem Account Number
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling!.InnerText) rem Meter Reading Start Date
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling!.InnerText)   rem Meter Reading End Date
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText) rem Billing Days
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.InnerText)  rem Counter Reading Start
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText)   rem Counter Reading End
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText)   rem Total HCF
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText)   rem Gallons
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText)   rem Payment Due Date
                        lviWaterBill.SubItems.Add(xnWaterBill.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText)  rem Amount Due

                        lvwWaterBills.Items.Add(lviWaterBill)

                        i++;
                    }
                }
            }
        }

        private sub Central_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        {
            ShowWaterBills()
        }

        private sub BtnCreateWaterBill_Click(sender As Object, e As EventArgs)
        {
            Create create = new()

            create.ShowDialog()

            ShowWaterBills()
        }

        private sub BtnViewWaterBill_Click(sender As Object, e As EventArgs)
        {
            Details details = new()

            details.ShowDialog()
        }

        private sub BtnEditWaterBill_Click(sender As Object, e As EventArgs)
        {
            Editor editor = new()

            if editor.ShowDialog() =MsgBoxResult.OK)
            {
                if string.IsNullOrEmpty(editor.TxtBillNumber.Text))
                {
                    MsgBox("You must first type a bill number and then click the Find Water Bill button. " +
                                    "You can then optionally change some values on the water bill and save it.",
                                    "Stellar Water Point", MessageBoxButtons.OK)
                    Exit Sub
                }

                rem Create an XML DOM object
                XmlDocument xdWaterBills = new XmlDocument()
                rem Prepare the path and name of the file that holds a list of water bills 
                string? strWaterBills = "C:\Stellar Water Point10\WaterBills.xml"

                rem Get the water bills records and store them in the above XML DOM object
                xdWaterBills.Load(strWaterBills)

                rem Create an XmlNodeList list that reprensents the XML elements from the list of water bills.
                 * Call the XML DOM's GetElementsByTagName() method. 
                 * To use the bill number elements as reference, pass the water bill number element as argument.
                XmlNodeList xnlWaterBills = xdWaterBills.DocumentElement!.GetElementsByTagName("bill-number")

                rem Visit each XML element of the list of water bills
                foreach (XmlNode xnWaterBill in xnlWaterBills)
                {
                    rem When you get to an element, find out if the value of its bill number is 
                    rem the same as the bill number the user typed in the form. If that's the case, 
                    rem change the value of each node of that element, using the values from the form.
                    if xnWaterBill.InnerText.Contains(editor.TxtBillNumber.Text))
                    {
                        xnWaterBill.ParentNode!.InnerXml =
                            "<bill-number>"              + editor.TxtBillNumber.Text            + "</bill-number>"                                   +
                            "<account-number>"           + editor.MtbAccountNumber.Text         + "</account-number>"                                +
                            "<meter-reading-start-date>" + editor.dtpMeterReadingStartDate.Value.ToShortDateString() + "</meter-reading-start-date>" +
                            "<meter-reading-end-date>"   + editor.dtpMeterReadingEndDate.Value.ToShortDateString()   + "</meter-reading-end-date>"   +
                            "<billing-days>"             + editor.TxtBillingDays.Text           + "</billing-days>"                                  +
                            "<counter-reading-start>"    + editor.TxtCounterReadingStart.Text   + "</counter-reading-start>"                         +
                            "<counter-reading-end>"      + editor.TxtCounterReadingEnd.Text     + "</counter-reading-end>"                           +
                            "<total-hcf>"                + editor.TxtTotalHCF.Text              + "</total-hcf>"                                     +
                            "<total-gallons>"            + editor.TxtTotalGallons.Text          + "</total-gallons>"                                 +
                            "<first-tier-consumption>"   + editor.TxtFirstTierConsumption.Text  + "</first-tier-consumption>"                        +
                            "<second-tier-consumption>"  + editor.TxtSecondTierConsumption.Text + "</second-tier-consumption>"                       +
                            "<last-tier-consumption>"    + editor.TxtLastTierConsumption.Text   + "</last-tier-consumption>"                         +
                            "<water-charges>"            + editor.TxtWaterCharges.Text          + "</water-charges>"                                 +
                            "<sewer-charges>"            + editor.TxtSewerCharges.Text          + "</sewer-charges>"                                 +
                            "<environment-charges>"      + editor.TxtEnvironmentCharges.Text    + "</environment-charges>"                           +
                            "<service-charges>"          + editor.TxtEnvironmentCharges.Text    + "</service-charges>"                               +
                            "<total-charges>"            + editor.TxtTotalCharges.Text          + "</total-charges>"                                 +
                            "<state-taxes>"              + editor.TxtStateTaxes.Text            + "</state-taxes>"                                   +
                            "<local-taxes>"              + editor.TxtLocalTaxes.Text            + "</local-taxes>"                                   +
                            "<payment-due-date>"         + editor.dtpPaymentDueDate.Value.ToShortDateString() + "</payment-due-date>"                +
                            "<amount-due>"               + editor.TxtAmountDue.Text             + "</amount-due>"                                    +
                            "<late-payment-due-date>"    + editor.dtpLatePaymentDueDate.Value.ToShortDateString() + "</late-payment-due-date>"       +
                            "<late-amount-due>"          + editor.TxtLateAmountDue.Text         + "</late-amount-due>"

                        rem After updating the elements, save the updated file
                        xdWaterBills.Save(strWaterBills)
                        rem After saving the file, stop searching
                        Exit For
                    }
                }
            }

            rem Now that the user has closed the Water Bill - Editor dialog box (and probably 
             rem updated the XML file for water bills), (re-)display the list of water bills.*/
            ShowWaterBills()
        }

        private sub BtnDeleteWaterBill_Click(sender As Object, e As EventArgs)
        {
            Delete delete = new()

            delete.ShowDialog()

            ShowWaterBills()
        }

        private sub BtnClose_Click(sender As Object, e As EventArgs)
        {
            Close()
        }
    }
}

To execute, on the main menu, click Debug -> Start Without Debugging:
On the Stellar Water Point form, click the Water Bills button
On the Water Bills form, click the Delete Water Bill button
In the Water Bill # text box, type 917829
Click Find Water Bill
Click Delete Water Bill
Read the message in the message box and click Yes:
Close the forms and return to your programming environment
From the Windows Explorer, open the WaterBills.xml file
Replace the content of the file with the provided file
Save the file
Return to your programming environment
Close Microsoft Visual Studio

Application


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