Introduction

The eXtensible Markup Language (XML) is one of the techniques you can use to create a text-based database application. The .NET Framework is wonderful library filled with all types of classes to explore XML, including creating, viewing, editing, deleting and managing nodes.

Practical Learning: Introducing the Application

1. Start Microsoft Visual Studio
2. Create a Windows Forms App named StellarWaterPoint2
3. To create a form, on the main menu, click Project -> Add Form (Windows Forms)...

Water Meters

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: Starting Water Meters Issues

1. To create a folder, in the Solution Explorer, right-click the StellarWaterPoint2 project -> Add -> New Folder
2. Type WaterMeters as the name of the folder
3. To create a form, in the Solution Explorer, right-click the new WaterMeters folder -> Add -> Form (Windows Forms)...
4. Type Create
5. Press Enter
6. Design the form as follows:

   

   Control		(Name)	Text	Other Properties
   Label			&Meter #:
   MaskedTextBox		mtbMeterNumber		Masked: 000-00-000
   Label			M&ake:
   TextBox		txtMake
   Label			M&odel:
   TextBox		txtModel		Modifiers: Public
   Label			Me&ter Size:
   TextBox		txtMeterSize
   Button		btnOK	&OK	DialogResult: OK
   Button		btnCancel	&Cancel	DialogResult: Cancel

7. 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

8. To create a form, in the Solution Explorer, right-click WaterMeters -> Add -> Form (Windows Forms)...
9. Type Details
10. Press Enter
11. Resize the Editor form to have the same size as the Create form
12. Copy everything from the Create form and paste it in the Editor form
13. Delete the bottom two buttons and add a new button
14. Change the design of the form as follows:

    

    Control		(Name)	Text
    Button		btnFindWateMeter	&Find Water Meter
    Button		btnClose	&Close

15. On the form, double-click the Find button
16. Return to the form and double-click the Close button
17. Change the document as follows:

    using System.Xml;
    
    namespace StellarWaterPoint.WaterMeters
    {
        public partial class Details : Form
        {
            public Details()
            {
                InitializeComponent();
            }
    
            private void btnFind_Click(object sender, EventArgs e)
            {
                XmlDocument xdWaterMeters = new XmlDocument();
                string? strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";
    
                FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);
    
                if (fiWaterMeters.Exists)
                {
                    using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        xdWaterMeters.Load(fsWaterMeters);
                        XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + mtbMeterNumber.Text + "']")!;
    
                        foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                        {
                            txtMake.Text      = xnWaterMeter.NextSibling!.InnerText;
                            txtModel.Text     = xnWaterMeter.NextSibling.NextSibling!.InnerText;
                            txtMeterSize.Text = xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText;
                        }
                    }
                }
            }
    
            private void btnClose_Click(object sender, EventArgs e)
            {
                Close();
            }
        }
    }

18. To create a form, in the Solution Explorer, right-click WaterMeters -> Add -> Form (Windows Forms)...
19. Type Editor
20. Press Enter
21. Resize the Editor form to have the same size as the Details form
22. Copy everything from the Details form and paste it in the Editor form
23. Change the design of the form as follows:

    

    Control		(Name)	Text
    Button		btnUpdateWateMeter	&Update Water Meter

24. On the form, double-click the Find button
25. Return to the form and double-click the Close button
26. Return to the form and double-click the Update Water Meter button
27. Change the document as follows:

    using System.Xml;
    
    namespace StellarWaterPoint.WaterMeters
    {
        public partial class Editor : Form
        {
            public Editor()
            {
                InitializeComponent();
            }
    
            private void btnFind_Click(object sender, EventArgs e)
            {
                XmlDocument xdWaterMeters = new XmlDocument();
                string? strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";
    
                FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);
    
                if (fiWaterMeters.Exists)
                {
                    using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        xdWaterMeters.Load(fsWaterMeters);
                        XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + mtbMeterNumber.Text + "']")!;
    
                        foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                        {
                            txtMake.Text = xnWaterMeter.NextSibling!.InnerText;
                            txtModel.Text = xnWaterMeter.NextSibling.NextSibling!.InnerText;
                            txtMeterSize.Text = xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText;
                        }
                    }
                }
            }
    
            private void btnUpdateWaterMeter_Click(object sender, EventArgs e)
            {
                XmlDocument xdWaterMeters = new XmlDocument();
                string? strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";
    
                FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);
    
                if (fiWaterMeters.Exists)
                {
                    using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        xdWaterMeters.Load(fsWaterMeters);
                        XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + mtbMeterNumber.Text + "']")!;
    
                        foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                        {
                            xnWaterMeter.ParentNode!.InnerXml = "<meter-number>" + mtbMeterNumber.Text + "</meter-number>" +
                                                                "<make>" + txtMake.Text + "</make>" +
                                                                "<model>" + txtModel.Text + "</model>" +
                                                                "<meter-size>" + txtMeterSize.Text + "</meter-size>";
                        }
                    }
    
                    using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.ReadWrite))
                    {
                        xdWaterMeters.Save(fsWaterMeters);
                    }
                }
    
                Close();
            }
    
            private void btnClose_Click(object sender, EventArgs e)
            {
                Close();
            }
        }
    }

28. To create a form, in the Solution Explorer, right-click WaterMeters -> Add -> Form(Windows Forms)...
29. Type Delete
30. Press Enter
31. Resize the Editor form to have the same size as the Editor form
32. Copy everything from the Editor form and paste it in the Delete form
33. Change the bottom button as follows:

    

    Control		(Name)	Text
    Button		btnDeleteWateMeter	&Delete Water Meter

34. On the form, double-click the Find button
35. Return to the form and double-click the Close button
36. Return to the form and double-click the Delete Water Meter button
37. Change the document as tollows:

    using System.Xml;
    
    namespace StellarWaterPoint.WaterMeters
    {
        public partial class Delete : Form
        {
            public Delete()
            {
                InitializeComponent();
            }
    
            private void btnFind_Click(object sender, EventArgs e)
            {
                XmlDocument xdWaterMeters = new XmlDocument();
                string? strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";
    
                FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);
    
                if (fiWaterMeters.Exists)
                {
                    using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        xdWaterMeters.Load(fsWaterMeters);
                        XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + mtbMeterNumber.Text + "']")!;
    
                        foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                        {
                            txtMake.Text = xnWaterMeter.NextSibling!.InnerText;
                            txtModel.Text = xnWaterMeter.NextSibling.NextSibling!.InnerText;
                            txtMeterSize.Text = xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText;
                        }
                    }
                }
            }
    
            private void btnDeleteWaterMeter_Click(object sender, EventArgs e)
            {
                XmlDocument xdWaterMeters = new XmlDocument();
                string? strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";
    
                if (string.IsNullOrEmpty(mtbMeterNumber.Text))
                {
                    MessageBox.Show("You must type a water meter number if you want to delete one.",
                                    "Stellar Water Point", MessageBoxButtons.OK, MessageBoxIcon.Information);
                    return;
                }
    
                if (!File.Exists(strWaterMeters))
                {
                    MessageBox.Show("There is no file for the water meters in the system.",
                                    "Stellar Water Point",
                                    MessageBoxButtons.OK, MessageBoxIcon.Information);
                    return;
                }
    
                xdWaterMeters.Load(strWaterMeters);
    
                XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.GetElementsByTagName("meter-number");
    
                foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                {
                    if (xnWaterMeter.InnerText == mtbMeterNumber.Text)
                    {
                        if (MessageBox.Show("Are you sure you want to delete this water meter record from the system?",
                                        "Stellar Water Point",
                                        MessageBoxButtons.YesNo, MessageBoxIcon.Question) == DialogResult.Yes)
                        {
                            xdWaterMeters.DocumentElement.RemoveChild(xnWaterMeter.ParentNode!);
                            break;
                        }
                    }
                }
    
                xdWaterMeters.Save(strWaterMeters);
    
                Close();
            }
    
            private void btnClose_Click(object sender, EventArgs e)
            {
                Close();
            }
        }
    }

38. To create a form, in the Solution Explorer, right-click WaterMeters -> Add -> Form (Windows Forms)...
39. Type Central
40. Press Enter
41. In the Toolbox, click the ListView button and click the form
42. On the form, right-click the list view and click Edit Columns...
43. Create the columns as follows:

    (Name)	Text	Width
    colWaterMeterId	Id	40
    colMeterNumber	Meter #	150
    colMake	Make	300
    colModel	Model	150
    colMeterSize	Meter Size	175

44. Click OK
45. Complete the design of the form as follows:

    

    Control		(Name)	Other Properties
    ListView		lvwWaterMeters	FullRowSelect: True GridLines: True View: Details Anchor: Top, Bottom, Left, Right
    Button		btnNewWaterMeter	&New Water Meter...
    Button		btnViewWaterMeter	&View Water Meter...
    Button		btnEditWaterMeter	&Edit Water Meter...
    Button		btnDeleteWateMeter	&Delete Water Meter

46. Doubte-click an unoccupied area of the form to generate its Load event
47. Return to the form and double-click the New Water Meter button
48. Return to the form and double-click the View Water Meter button
49. Return to the form and double-click the Edit Water Meter button
50. Return to the form and double-click the Delete Water Meter button
51. Return to the form and double-click the Close button
52. Change the document as follows:

    using System.Xml;
    
    namespace StellarWaterPoint.WaterMeters
    {
        public partial class Central : Form
        {
            public Central()
            {
                InitializeComponent();
            }
    
            private void ShowWaterMeters()
            {
                lvwWaterMeters.Items.Clear();
    
                XmlDocument xdWaterMeters  = new XmlDocument();
                string?     strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";
    
                FileInfo?   fiWaterMeters  = new FileInfo(strWaterMeters);
    
                if (fiWaterMeters.Exists)
                {
                    using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        xdWaterMeters.Load(fsWaterMeters);
                        XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.ChildNodes;
                        
                        int i = 1;
    
                        foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                        {
                            ListViewItem lviWaterMeter = 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);
    
                            lvwWaterMeters.Items.Add(lviWaterMeter);
    
                            i++;
                        }
                    }
                }
            }
    
            private void Central_Load(object sender, EventArgs e)
            {
                ShowWaterMeters();
            }
    
            private void btnNewWaterMeter_Click(object sender, EventArgs e)
            {
                Create      wm            = new();
                FileInfo?   fiWaterMeters = null;
                FileStream? fsWaterMeters = null;
                XmlDocument xdWaterMeters = new XmlDocument();
                string?     strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";
    
                if (wm.ShowDialog() == DialogResult.OK)
                {
                    fiWaterMeters = new FileInfo(strWaterMeters);
    
                    if (fiWaterMeters.Exists)
                    {
                        using (fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                        {
                            xdWaterMeters.Load(fsWaterMeters);
                        }
                    }
                    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);
                        }
                    }
    
                    using (fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.ReadWrite))
                    {
                        XmlElement xeWaterMeter = xdWaterMeters.CreateElement("water-meter");
    
                        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>";
                        xdWaterMeters.DocumentElement!.AppendChild(xeWaterMeter);
                        xdWaterMeters.Save(fsWaterMeters);
                    }
                }
    
                ShowWaterMeters();
            }
    
            private void btnViewWaterMeter_Click(object sender, EventArgs e)
            {
                Details editor = new();
    
                editor.ShowDialog();
            }
    
            private void btnEditWaterMeter_Click(object sender, EventArgs e)
            {
                Editor editor = new();
    
                editor.ShowDialog();
    
                ShowWaterMeters();
            }
    
            private void btnDeleteWaterMeter_Click(object sender, EventArgs e)
            {
                Delete delete = new();
    
                delete.ShowDialog();
    
                ShowWaterMeters();
            }
    
            private void btnClose_Click(object sender, EventArgs e)
            {
                Close();
            }
        }
    }

Customers

Obviously, customers are the ones who use the services of the bussiness whose application we are builduing. Obviously, a customers represented by a business account, and a water meter must be associated to a customer's account. As seen with water meterrs, the application with use forms to create and manage customers accounts.

Practical Learning: Preparing Customers Accounts

1. In the Solution Explorer, right-click the StellarWaterPoint1 project -> Add -> New Folder
2. Type Customers as the name of the folder
3. To create a form, on the main menu, click Customers -> Add -> Form (Windows Forms)...
4. Type Create as the name of the file
5. Click Add
6. Design the form as follows:

   

   Control		(Name)	Text	Other Properties
   Label			&Account #:
   MaskedTextBox		mtbAccountNumber		Masked: 0000-000-0000
   Label			&Meter #:
   MaskedTextBox		mtbMeterNumber		Masked: 000-00-000
   Button		btnFindWaterMeter	&Find Water Meter
   Label			Meter &Details:
   TextBox		txtMeterDetails
   Label			&First Name:
   TextBox		txtFirstName
   Label			&Last Name:
   TextBox		txtLastName
   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
   Button		btnClose	&Close

7. 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:    btnCancel

8. On the form, double-click the Find Water Meter button
9. Change the document as follows:

   using System.Xml;
   
   namespace StellarWaterPoint.Customers
   {
       public partial class Create : Form
       {
           public Create()
           {
               InitializeComponent();
           }
   
           private void btnFindWaterMeter_Click(object sender, EventArgs e)
           {
               XmlDocument xdWaterMeters = new XmlDocument();
               string? strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";
   
               FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);
   
               if (fiWaterMeters.Exists)
               {
                   using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                   {
                       xdWaterMeters.Load(fsWaterMeters);
                       XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + mtbMeterNumber.Text + "']")!;
   
                       foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                       {
                           txtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " + 
                                                  xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " + 
                                                  xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")";
                       }
                   }
               }
           }
       }
   }

10. To create a form, in the Solution Explorer, right-click Customers -> Add -> Form (Windows Forms)...
11. Type Details
12. Press Enter
13. Resize the Editor form to have the same size as the Create form
14. Copy everything from the Create form and paste it in the Editor form
15. Delete the bottom two buttons and add a new button
16. Change the design of the form as follows:

    

    Control		(Name)	Other Properties
    Button		btnFindCustomerAccount	&Find Customer Account
    Button		btnClose	&Close

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

    FormBorderStyle: FixedDialog
    Text:            Stellar Water Point - Customer Account Details
    StartPosition:   CenterScreen
    CancelButton:    btnClose

18. On the form, double-click the Find Customer Account
19. Return to the form and double-click the Close button
20. Change the document as follows:

    using System.Xml;
    
    namespace StellarWaterPoint.Customers
    {
        public partial class Details : Form
        {
            public Details()
            {
                InitializeComponent();
            }
    
            private void btnFindCustomerAccount_Click(object sender, EventArgs e)
            {
                XmlDocument xdCustomers = new XmlDocument();
                string? strCustomers = @"C:\Stellar Water Point\Customers.xml";
    
                FileInfo? fiCustomers = new FileInfo(strCustomers);
    
                if (fiCustomers.Exists)
                {
                    using (FileStream? fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        xdCustomers.Load(fsCustomers);
                        XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + mtbAccountNumber.Text + "']")!;
    
                        foreach (XmlNode xnCustomer in xnlCustomers)
                        {
                            mtbMeterNumber.Text = xnCustomer.NextSibling!.InnerText;   // Meter #
                            txtFirstName.Text   = xnCustomer.NextSibling.NextSibling!.InnerText; // First Name
                            txtLastName.Text    = xnCustomer.NextSibling.NextSibling.NextSibling!.InnerText;   // Last Name
                            txtAddress.Text     = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;   // Address
                            txtCity.Text        = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.InnerText;   // City
                            txtCounty.Text      = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText;   // County
                            txtState.Text       = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;   // State
                            mtbZIPCode.Text     = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText; // ZIP-Code
                        }
                    }
                }
    
                XmlDocument xdWaterMeters = new XmlDocument();
                string? strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";
    
                FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);
    
                if (fiWaterMeters.Exists)
                {
                    using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        xdWaterMeters.Load(fsWaterMeters);
                        XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + mtbMeterNumber.Text + "']")!;
    
                        foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                        {
                            txtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                                   xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                                   xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")";
                        }
                    }
                }
            }
        }
    }

21. To create a form, in the Solution Explorer, right-click Customers -> Add -> Form (Windows Forms)...
22. Type Editor
23. Press Enter
24. Resize the Editor form to have the same size as the Create form
25. Copy everything from the Create form and paste it in the Editor form
26. Change the design as follows:

    

    Control		(Name)	Text	Other Properties
    Button		btnFindCustomerAccount	&Find Customer Account
    Button		btnFindWaterMeter	&Find Water Meter
    Button		btnUpdateCustomerAccount	&Update Customer Account
    Button		btnCancel	&Cancel	DialogResult: Cancel

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

    FormBorderStyle: FixedDialog
    Text:            Stellar Water Point - Customer Account Editor
    StartPosition:   CenterScreen
    CancelButton:    btnCancel

28. On the form, double-click the Find Customer Account
29. Return to the form and double-click the Find Water Meter button
30. Return to the form and double-click the Update Water Meter button
31. Change the document as tollows:

    using System.Xml;
    
    namespace StellarWaterPoint.Customers
    {
        public partial class Editor : Form
        {
            public Editor()
            {
                InitializeComponent();
            }
    
            private void btnFindCustomerAccount_Click(object sender, EventArgs e)
            {
                XmlDocument xdCustomers  = new XmlDocument();
                string?     strCustomers = @"C:\Stellar Water Point\Customers.xml";
    
                FileInfo?   fiCustomers  = new FileInfo(strCustomers);
    
                if (fiCustomers.Exists)
                {
                    using (FileStream? fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        xdCustomers.Load(fsCustomers);
                        XmlNodeList xnlCustomers   = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + mtbAccountNumber.Text + "']")!;
    
                        foreach (XmlNode xnCustomer in xnlCustomers)
                        {
                            mtbMeterNumber.Text = xnCustomer.NextSibling!.InnerText;   // Meter #
                            txtFirstName.Text   = xnCustomer.NextSibling.NextSibling!.InnerText; // First Name
                            txtLastName.Text    = xnCustomer.NextSibling.NextSibling.NextSibling!.InnerText;   // Last Name
                            txtAddress.Text     = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;   // Address
                            txtCity.Text        = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.InnerText;   // City
                            txtCounty.Text      = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText;   // County
                            txtState.Text       = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;   // State
                            mtbZIPCode.Text     = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText; // ZIP-Code
                        }
                    }
                }
    
                XmlDocument xdWaterMeters  = new XmlDocument();
                string?     strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";
    
                FileInfo?   fiWaterMeters  = new FileInfo(strWaterMeters);
    
                if (fiWaterMeters.Exists)
                {
                    using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        xdWaterMeters.Load(fsWaterMeters);
                        XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + mtbMeterNumber.Text + "']")!;
    
                        foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                        {
                            txtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                                   xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                                   xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")";
                        }
                    }
                }
            }
    
            private void btnFindWaterMeter_Click(object sender, EventArgs e)
            {
                XmlDocument xdWaterMeters  = new XmlDocument();
                string?     strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";
    
                FileInfo? fiWaterMeters    = new FileInfo(strWaterMeters);
    
                if (fiWaterMeters.Exists)
                {
                    using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        xdWaterMeters.Load(fsWaterMeters);
                        XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + mtbMeterNumber.Text + "']")!;
    
                        foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                        {
                            txtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                                   xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                                   xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")";
                        }
                    }
                }
            }
    
            private void btnUpdateCustomerAccount_Click(object sender, EventArgs e)
            {
                XmlDocument xdCustomers = new XmlDocument();
                string? strCustomers    = @"C:\Stellar Water Point\Customers.xml";
    
                FileInfo? fiCustomers   = new FileInfo(strCustomers);
    
                if (fiCustomers.Exists)
                {
                    using (FileStream? fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        xdCustomers.Load(fsCustomers);
                        XmlNodeList xnlCustomers   = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + mtbAccountNumber.Text + "']")!;
    
                        foreach (XmlNode xnCustomer in xnlCustomers)
                        {
                            xnCustomer.ParentNode!.InnerXml = "<account-number>" + mtbAccountNumber.Text + "</account-number>" +
                                                              "<meter-number>"   + mtbMeterNumber.Text   + "</meter-number>"   +
                                                              "<first-name>"     + txtFirstName.Text     + "</first-name>"     +
                                                              "<last-name>"      + txtLastName.Text      + "</last-name>"      +
                                                              "<address>"        + txtAddress.Text       + "</address>"        +
                                                              "<city>"           + txtCity.Text          + "</city>"           +
                                                              "<county>"         + txtCounty.Text        + "</county>"         +
                                                              "<state>"          + txtState.Text         + "</state>"          +
                                                              "<zip-code>"       + mtbZIPCode.Text       + "</zip-code>";
                        }
                    }
    
                    using (FileStream? fsCustomers = new FileStream(fiCustomers.FullName, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.ReadWrite))
                    {
                        xdCustomers.Save(fsCustomers);
                    }
                }
    
                Close();
            }
        }
    }

32. To create a form, in the Solution Explorer, right-click Customers -> Add -> Form (Windows Forms)...
33. Type Delete
34. Press Enter
35. Resize the Editor form to have the same size as the Editor form
36. Copy everything from the Editor form and paste it in the Delete form
37. Delete the Find Water Meter button and change the bottom button as follows:

    

    Control		(Name)	Text
    Button		btnDeleteCustomerAccount	&Delete Customer Account

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

    FormBorderStyle: FixedDialog
    Text:            Stellar Water Point - Customer Account Deletion
    StartPosition:   CenterScreen
    CancelButton:    btnCancel

39. On the form, double-click the Find Customer Account
40. Return to the form and double-click the Delete Water Meter button
41. Change the document as tollows:

    using System.Xml;
    
    namespace StellarWaterPoint.Customers
    {
        public partial class Delete : Form
        {
            public Delete()
            {
                InitializeComponent();
            }
    
            private void btnFindCustomerAccount_Click(object sender, EventArgs e)
            {
                XmlDocument xdCustomers = new XmlDocument();
                string? strCustomers = @"C:\Stellar Water Point\Customers.xml";
    
                FileInfo? fiCustomers = new FileInfo(strCustomers);
    
                if (fiCustomers.Exists)
                {
                    using (FileStream? fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        xdCustomers.Load(fsCustomers);
                        XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + mtbAccountNumber.Text + "']")!;
    
                        foreach (XmlNode xnCustomer in xnlCustomers)
                        {
                            mtbMeterNumber.Text = xnCustomer.NextSibling!.InnerText;   // Meter #
                            txtFirstName.Text   = xnCustomer.NextSibling.NextSibling!.InnerText; // First Name
                            txtLastName.Text    = xnCustomer.NextSibling.NextSibling.NextSibling!.InnerText;   // Last Name
                            txtAddress.Text     = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;   // Address
                            txtCity.Text        = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.InnerText;   // City
                            txtCounty.Text      = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText;   // County
                            txtState.Text       = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;   // State
                            mtbZIPCode.Text     = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText; // ZIP-Code
                        }
                    }
                }
    
                XmlDocument xdWaterMeters = new XmlDocument();
                string? strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";
    
                FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);
    
                if (fiWaterMeters.Exists)
                {
                    using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        xdWaterMeters.Load(fsWaterMeters);
                        XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + mtbMeterNumber.Text + "']")!;
    
                        foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                        {
                            txtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                                   xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                                   xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")";
                        }
                    }
                }
            }
    
            private void btnDeleteCustomerAccount_Click(object sender, EventArgs e)
            {
                XmlDocument xdCustomers = new XmlDocument();
                string? strCustomers = @"C:\Stellar Water Point\Customers.xml";
    
                if (string.IsNullOrEmpty(mtbAccountNumber.Text))
                {
                    MessageBox.Show("You must type an account number for the customer whose account you want to deleteone.",
                                    "Stellar Water Point", MessageBoxButtons.OK, MessageBoxIcon.Information);
                    return;
                }
    
                if (!File.Exists(strCustomers))
                {
                    MessageBox.Show("There is no file for the customers accounts in the system.",
                                    "Stellar Water Point",
                                    MessageBoxButtons.OK, MessageBoxIcon.Information);
                    return;
                }
    
                xdCustomers.Load(strCustomers);
    
                XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.GetElementsByTagName("account-number");
    
                foreach (XmlNode xnCustomer in xnlCustomers)
                {
                    if (xnCustomer.InnerText == mtbAccountNumber.Text)
                    {
                        if (MessageBox.Show("Are you sure you want to remove this customer's account from the system?",
                                        "Stellar Water Point",
                                        MessageBoxButtons.YesNo, MessageBoxIcon.Question) == DialogResult.Yes)
                        {
                            xdCustomers.DocumentElement.RemoveChild(xnCustomer.ParentNode!);
                            break;
                        }
                    }
                }
    
                xdCustomers.Save(strCustomers);
    
                Close();
            }
        }
    }

42. To create a form, in the Solution Explorer, right-click Models -> Add -> Form (Windows Forms)...
43. Type Central
44. Press Enter
45. In the Toolbox, click the ListView button and click the form
46. On the form, right-click the list view and click Edit Columns...
47. Create the columns as follows:

    (Name)	Text	TextAlign	Width
    colCustomerId	Id		40
    colAccountNumber	Account #	Center	150
    colMeterNumber	Meter #	Center	120
    colFirstName	First Name		135
    colLastName	Last Name		135
    colAddress	Address		250
    colCity	City		125
    colCounty	County		135
    colState	State	Center
    colZIPCode	ZIP-Code	Center	125

48. Click OK
49. Complete the design of the form as follows:

    

    Control		(Name)	Text	Other Properties
    ListView		lvwCustomers		FullRowSelect: True GridLines: True View: Details Anchor: Top, Bottom, Left, Right
    Button		btnNewCustomerAccount	&New Customer Account...	Anchor: Bottom, Right
    Button		btnViewCustomerAccount	&View Customer Account...	Anchor: Bottom, Right
    Button		btnEditCustomerAccount	&Edit Customer Account...	Anchor: Bottom, Right
    Button		btnDeleteCustomerAccount	&Delete Customer Account...	Anchor: Bottom, Right
    Button		btnClose	&Close	Anchor: Bottom, Right

50. Doubte-click an unoccupied area of the form to generate its Load event
51. Return to the form and double-click the New Customer Account button
52. Return to the form and double-click the View Customer Account button
53. Return to the form and double-click the Edit Customer Account button
54. Return to the form and double-click the Delete Customer Account button
55. Return to the form and double-click the Close button
56. Change the document as follows:

    using System.Xml;
    
    namespace StellarWaterPoint.Customers
    {
        public partial class Central : Form
        {
            public Central()
            {
                InitializeComponent();
            }
    
            private void ShowCustomers()
            {
                int i = 1;
    
                lvwCustomers.Items.Clear();
    
                XmlDocument xdCustomers = new XmlDocument();
                string? strCustomers = @"C:\Stellar Water Point\Customers.xml";
    
                FileInfo? fiCustomers = new FileInfo(strCustomers);
    
                if (fiCustomers.Exists)
                {
                    using (FileStream? fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        xdCustomers.Load(fsCustomers);
                        XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.ChildNodes;
    
                        foreach (XmlNode xnCustomer in xnlCustomers)
                        {
                            ListViewItem lviCustomer = new ListViewItem(i.ToString());
    
                            lviCustomer.SubItems.Add(xnCustomer.FirstChild!.InnerText);   // Account #
                            lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling!.InnerText);   // Meter #
                            lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling!.InnerText); // First Name
                            lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling!.InnerText);   // Last Name
                            lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText);   // Address
                            lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.InnerText);   // City
                            lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText);   // County
                            lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText);   // State
                            lviCustomer.SubItems.Add(xnCustomer.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText); // ZIP-Code
    
                            lvwCustomers.Items.Add(lviCustomer);
    
                            i++;
                        }
                    }
                }
            }
    
            private void Central_Load(object sender, EventArgs e)
            {
                ShowCustomers();
            }
    
            private void btnNewCustomerAccount_Click(object sender, EventArgs e)
            {
                FileInfo? fiCustomers = null;
                FileStream? fsCustomers = null;
                Create create = new Create();
                XmlDocument xdCustomers = new XmlDocument();
                string? strCustomers = @"C:\Stellar Water Point\Customers.xml";
    
                if (create.ShowDialog() == DialogResult.OK)
                {
                    fiCustomers = new FileInfo(strCustomers);
    
                    if (fiCustomers.Exists)
                    {
                        using (fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                        {
                            xdCustomers.Load(fsCustomers);
                        }
                    }
                    else
                    {
                        using (fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Create, FileAccess.Write, FileShare.Write))
                        {
                            xdCustomers.LoadXml("<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
                                                  "<customers></customers>");
                            xdCustomers.Save(fsCustomers);
                        }
                    }
    
                    using (fsCustomers = new FileStream(fiCustomers.FullName, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.ReadWrite))
                    {
                        XmlElement xeCustomer = xdCustomers.CreateElement("customer");
    
                        xeCustomer.InnerXml = "<account-number>" + create.mtbAccountNumber.Text + "</account-number>" +
                                                "<meter-number>" + create.mtbMeterNumber.Text   + "</meter-number>"   +
                                                "<first-name>"   + create.txtFirstName.Text     + "</first-name>"     +
                                                "<last-name>"    + create.txtLastName.Text      + "</last-name>"      +
                                                "<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();
            }
    
            private void btnViewCustomerAccount_Click(object sender, EventArgs e)
            {
                Details editor = new Details();
    
                editor.ShowDialog();
            }
    
            private void btnEditCustomerAccount_Click(object sender, EventArgs e)
            {
                Editor editor = new Editor();
    
                editor.ShowDialog();
    
                ShowCustomers();
            }
    
            private void btnDeleteCustomerAccount_Click(object sender, EventArgs e)
            {
                Delete delete = new Delete();
    
                delete.ShowDialog();
    
                ShowCustomers();
            }
    
            private void btnClose_Click(object sender, EventArgs e)
            {
                Close();
            }
        }
    }

Water Bills

A water bill is a summary that indicates how much water a customer consumed and the value of that consumption. Our application will include a form to process a water bill. We will use another form that can be used to review an existing water bill. We will use another form to change or update a water bill that was previously processed. Finally, we will have a form that can be used to delete a water bill. In previous sections, we provided one Central form for the water meters and another Central form for the Customers. Those Central forms allow the user to navigate to the forms related to a section. Those sections included a form that provides a list of records. Because a water bill has too many values, we will not create a form that presents a list of water bills.

Practical Learning: Preparing Bills

1. In the Solution Explorer, right-click StellarWaterPoint1 -> Add -> New Folder
2. Type WaterBills as the name of the folder
3. To create a form, in the Solution Explorer, right-click WaterBills -> Add -> Form (Windows Forms)...
4. Type Create as the name of the file
5. Press Enter
6. Design the form as follows:

   

   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

7. On the form, double-click the Find Customer Account button
8. Return to the Water Bills - Create form and double-click the Meter Reading End Date date time picker
9. Return to the Water Bills - Create form and double-click the Evaluate Water Bill button
10. Return to the Water Bills - Create form and double-click the Save Water Bill button
11. Return to the form and double-click the Close button
12. Change the document as follows:

    using System.Xml;
    
    namespace StellarWaterPoint.WaterBills
    {
        public partial class Create : Form
        {
            public Create()
            {
                InitializeComponent();
            }
    
            private void btnFindCustomerAccount_Click(object sender, EventArgs e)
            {
                string? strMeterNumber = null;
                XmlDocument xdCustomers = new XmlDocument();
                string? strCustomers = @"C:\Stellar Water Point\Customers.xml";
    
                FileInfo? fiCustomers = new FileInfo(strCustomers);
    
                if (fiCustomers.Exists)
                {
                    using (FileStream? fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        xdCustomers.Load(fsCustomers);
                        XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + mtbAccountNumber.Text + "']")!;
    
                        foreach (XmlNode xnCustomer in xnlCustomers)
                        {
                            strMeterNumber       = xnCustomer.NextSibling!.InnerText;   // Meter #
                            txtCustomerName.Text = xnCustomer.NextSibling.NextSibling!.InnerText + " " +
                                                   xnCustomer.NextSibling.NextSibling.NextSibling!.InnerText;   // Customer Name
                            txtAddress.Text      = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;   // Address
                            txtCity.Text         = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.InnerText;   // City
                            txtCounty.Text       = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText;   // County
                            txtState.Text        = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;   // State
                            mtbZIPCode.Text      = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText; // ZIP-Code
                        }
                    }
                }
    
                XmlDocument xdWaterMeters  = new XmlDocument();
                string?     strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";
    
                FileInfo?   fiWaterMeters  = new FileInfo(strWaterMeters);
    
                if (fiWaterMeters.Exists)
                {
                    using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        xdWaterMeters.Load(fsWaterMeters);
                        XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;
    
                        foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                        {
                            txtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                                   xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                                   xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")";
                        }
                    }
                }
            }
    
            private void dtpMeterReadingEndDate_ValueChanged(object sender, EventArgs e)
            {
                TimeSpan tsDays = dtpMeterReadingEndDate.Value - dtpMeterReadingStartDate.Value;
    
                txtBillingDays.Text = tsDays.Days.ToString();
            }
    
            private void btnEvaluateWaterBill_Click(object sender, EventArgs e)
            {
                double counterStart = 0, counterEnd = 0;
    
                try
                {
                    counterStart = double.Parse(txtCounterReadingStart.Text);
                }
                catch (FormatException feCRStart)
                {
                    MessageBox.Show("There was a problem with the value of the " +
                                    "Counter Reading Start. The error produced is: " + feCRStart.Message,
                                    "Stellar Water Point", MessageBoxButtons.OK, MessageBoxIcon.Information);
                }
    
                try
                {
                    counterEnd = double.Parse(txtCounterReadingEnd.Text);
                }
                catch (FormatException feCREnd)
                {
                    MessageBox.Show("There was a problem with the value of the " +
                                    "Counter Reading End. The error produced is: " + feCREnd.Message,
                                    "Stellar Water Point", MessageBoxButtons.OK, MessageBoxIcon.Information);
                }
    
                double consumption  = counterEnd   - counterStart;
                double gallons      = consumption  * 748.05;
                double firstTier    = gallons      * (48.00 / 10000.00);
                double secondTier   = gallons      * (32.00 / 10000.00);
                double lastTier     = gallons      * (20.00 / 10000.00);
                double waterCharges = firstTier    + secondTier + lastTier;
                double sewerCharges = waterCharges * 28.65 / 100;
                double envCharges   = waterCharges * 0.22184;
                double totalCharges = waterCharges + sewerCharges + envCharges;
                double localTaxes   = totalCharges * 0.06148;
                double stateTaxes   = totalCharges * 0.01374;
                double amtDue       = totalCharges + localTaxes + stateTaxes;
    
                TimeSpan tsPaymentDueDate = new TimeSpan(15, 0, 0, 0);
    
                txtTotalCCF.Text              = consumption.ToString();
                txtTotalGallons.Text          = gallons.ToString("F");
                txtFirstTierConsumption.Text  = firstTier.ToString("F");
                txtSecondTierConsumption.Text = secondTier.ToString("F");
                txtLastTierConsumption.Text   = lastTier.ToString("F");
                txtWaterCharges.Text          = waterCharges.ToString("F");
                txtSewerCharges.Text          = sewerCharges.ToString("F");
                txtEnvironmentCharges.Text    = envCharges.ToString("F");
                txtTotalCharges.Text          = totalCharges.ToString("F");
                txtLocalTaxes.Text            = localTaxes.ToString("F");
                txtStateTaxes.Text            = stateTaxes.ToString("F");
                dtpPaymentDueDate.Value       = dtpMeterReadingEndDate.Value + tsPaymentDueDate;
                txtAmountDue.Text             = amtDue.ToString("F");
                dtpLatePaymentDueDate.Value   = dtpMeterReadingEndDate.Value + new TimeSpan(30, 0, 0, 0);
                txtLateAmountDue.Text         = (amtDue + 8.95).ToString("F");
            }
    
            private void btnSaveWaterBill_Click(object sender, EventArgs e)
            {
                if (string.IsNullOrEmpty(txtBillNumber.Text))
                {
                    MessageBox.Show("You must type a bill number." +
                                    "Otherwise, the account cannot be saved.",
                                    "Stellar Water Point", MessageBoxButtons.OK);
                    return;
                }
    
                if (string.IsNullOrEmpty(txtCounterReadingStart.Text))
                {
                    MessageBox.Show("You must enter the start value of the water bill counter." +
                                    "Otherwise, the account cannot be saved.",
                                    "Stellar Water Point", MessageBoxButtons.OK);
                    return;
                }
    
                if (string.IsNullOrEmpty(mtbAccountNumber.Text))
                {
                    MessageBox.Show("You must type an account number of a customer." +
                                    "Otherwise, the account cannot be saved.",
                                    "Stellar Water Point", MessageBoxButtons.OK);
                    return;
                }
    
                FileStream? fsWaterBills = null;
                XmlDocument xdWaterBills = new XmlDocument();
                string strWaterBills = @"C:\Stellar Water Point\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-d ate>"  + 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-gallons>"            + txtTotalGallons.Text          + "</total-gallons>"           +
                                           "<total-ccf>"                + txtTotalCCF.Text              + "</total-ccf>"               +
                                           "<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>"     +
                                           "<total-charges>"            + txtTotalCharges.Text          + "</total-charges>"           +
                                           "<local-taxes>"              + txtLocalTaxes.Text            + "</local-taxes>"             +
                                           "<state-taxes>"              + txtStateTaxes.Text            + "</state-taxes>"             +
                                           "<amount-due>"               + txtAmountDue.Text             + "</amount-due>"              +
                                           "<payment-due-date>"         + dtpPaymentDueDate.Value.ToShortDateString()                  + "</payment-due-date>" +
                                           "<late-amount-due>"          + txtLateAmountDue.Text         + "</late-amount-due>"         +
                                           "<late-payment-due-date>"    + dtpLatePaymentDueDate.Value.ToShortDateString()              + "</late-payment-due-date>";
                    
                    xdWaterBills.DocumentElement!.AppendChild(xeWaterBill);
                    xdWaterBills.Save(fsWaterBills);
                }
    
                Close();
            }
    
            private void btnClose_Click(object sender, EventArgs e)
            {
                Close();
            }
        }
    }

13. To create a new form, in the Solution Explorer, right-click Water Bills -> New -> Form (Windows Forms)...
14. Type Details as the name of the form
15. Click Add
16. Make that form the same size as the Create Water Bill form
17. Select everything on the Create Water Bill form. Copy that selection and paste it in the new Water Bill - Details form
18. On the Water Bill - Details form, delete the Find Customer Account, the Evaluate Water Bill, and the Save Water Bill buttons
19. Add a button as follows:

    

    Control		(Name)	Text
    Button		btnFindWaterBill	Find Water &Bill

20. On the form, double-click the Find Water Bill button
21. Return tp the form and double-click the Close button
22. Change the document as follows:

    using System.Xml;
    
    namespace StellarWaterPoint.WaterBills
    {
        public partial class Details : Form
        {
            public Details()
            {
                InitializeComponent();
            }
    
            private void btnFindWaterBill_Click(object sender, EventArgs e)
            {
                if (string.IsNullOrEmpty(txtBillNumber.Text))
                {
                    MessageBox.Show("You must type a bill number." +
                                    "Otherwise, the account cannot be saved.",
                                    "Stellar Water Point", MessageBoxButtons.OK);
                    return;
                }
    
                string? strMeterNumber = null;
    
                FileStream? fsWaterBills = null;
                XmlDocument xdWaterBills = new XmlDocument();
                string strWaterBills = @"C:\Stellar Water Point\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);
                        XmlNodeList xnlWaterBills = xdWaterBills.DocumentElement!.SelectNodes("//bill-number[.='" + txtBillNumber.Text + "']")!;
    
                        foreach (XmlNode xnWaterBill in xnlWaterBills)
                        {
                            mtbAccountNumber.Text          =                xnWaterBill.NextSibling!.InnerText;
                            dtpMeterReadingStartDate.Value = DateTime.Parse(xnWaterBill.NextSibling!.NextSibling!.InnerText); 
                            dtpMeterReadingEndDate.Value   = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling!.InnerText);
                            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;
                            txtTotalGallons.Text           =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText;
                            txtTotalCCF.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;
                            txtTotalCharges.Text           =                xnWaterBill.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!.InnerText;
                            txtStateTaxes.Text             =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                            txtAmountDue.Text              =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                            dtpPaymentDueDate.Value        = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText);
                            txtLateAmountDue.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                            dtpLatePaymentDueDate.Value    = 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);
                        }
                    }
                }
    
                XmlDocument xdCustomers = new XmlDocument();
                string? strCustomers = @"C:\Stellar Water Point\Customers.xml";
    
                FileInfo? fiCustomers = new FileInfo(strCustomers);
    
                if (fiCustomers.Exists)
                {
                    using (FileStream? fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        xdCustomers.Load(fsCustomers);
                        XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + mtbAccountNumber.Text + "']")!;
    
                        foreach (XmlNode xnCustomer in xnlCustomers)
                        {
                            strMeterNumber       = xnCustomer.NextSibling!.InnerText;   // Meter #
                            txtCustomerName.Text = xnCustomer.NextSibling.NextSibling!.InnerText + " " +
                                                   xnCustomer.NextSibling.NextSibling.NextSibling!.InnerText;   // Customer Name
                            txtAddress.Text      = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;   // Address
                            txtCity.Text         = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.InnerText;   // City
                            txtCounty.Text       = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText;   // County
                            txtState.Text        = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;   // State
                            mtbZIPCode.Text      = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText; // ZIP-Code
                        }
                    }
                }
    
                XmlDocument xdWaterMeters = new XmlDocument();
                string? strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";
    
                FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);
    
                if (fiWaterMeters.Exists)
                {
                    using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        xdWaterMeters.Load(fsWaterMeters);
                        XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;
    
                        foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                        {
                            txtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                                   xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                                   xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")";
                        }
                    }
                }
            }
    
            private void btnClose_Click(object sender, EventArgs e)
            {
                Close();
            }
        }
    }

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

    

    Control		(Name)	Text
    Button		btnUpdateWaterBill	&Update Water Bill

30. On the form, double-click the Find Water Bill button
31. Return tp the form and double-click the Find Customer Account button
32. Return tp the form and double-click the Meter Reading End Date date time picker
33. Return tp the form and double-click the Evaluate Water Bill button
34. Return tp the form and double-click the Update Water Bill button
35. Return tp the form and double-click the Close button
36. Change the document as follows:

    using System.Xml;
    
    namespace StellarWaterPoint.WaterBills
    {
        public partial class Editor : Form
        {
            public Editor()
            {
                InitializeComponent();
            }
    
            private void btnFindWaterBill_Click(object sender, EventArgs e)
            {
                if (string.IsNullOrEmpty(txtBillNumber.Text))
                {
                    MessageBox.Show("You must type a bill number." +
                                    "Otherwise, the account cannot be saved.",
                                    "Stellar Water Point", MessageBoxButtons.OK);
                    return;
                }
    
                string? strMeterNumber = null;
    
                FileStream? fsWaterBills = null;
                XmlDocument xdWaterBills = new XmlDocument();
                string strWaterBills = @"C:\Stellar Water Point\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);
                        XmlNodeList xnlWaterBills = xdWaterBills.DocumentElement!.SelectNodes("//bill-number[.='" + txtBillNumber.Text + "']")!;
    
                        foreach (XmlNode xnWaterBill in xnlWaterBills)
                        {
                            mtbAccountNumber.Text          =                xnWaterBill.NextSibling!.InnerText;
                            dtpMeterReadingStartDate.Value = DateTime.Parse(xnWaterBill.NextSibling!.NextSibling!.InnerText);
                            dtpMeterReadingEndDate.Value   = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling!.InnerText);
                            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;
                            txtTotalGallons.Text           =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText;
                            txtTotalCCF.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;
                            txtTotalCharges.Text           =                xnWaterBill.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!.InnerText;
                            txtStateTaxes.Text             =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                            txtAmountDue.Text              =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                            dtpPaymentDueDate.Value        = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText);
                            txtLateAmountDue.Text          =                xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                            dtpLatePaymentDueDate.Value    = 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);
                        }
                    }
                }
    
                XmlDocument xdCustomers = new XmlDocument();
                string? strCustomers = @"C:\Stellar Water Point\Customers.xml";
    
                FileInfo? fiCustomers = new FileInfo(strCustomers);
    
                if (fiCustomers.Exists)
                {
                    using (FileStream? fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        xdCustomers.Load(fsCustomers);
                        XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + mtbAccountNumber.Text + "']")!;
    
                        foreach (XmlNode xnCustomer in xnlCustomers)
                        {
                            strMeterNumber       = xnCustomer.NextSibling!.InnerText;   // Meter #
                            txtCustomerName.Text = xnCustomer.NextSibling.NextSibling!.InnerText + " " +
                                                   xnCustomer.NextSibling.NextSibling.NextSibling!.InnerText;   // Last Name
                            txtAddress.Text      = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;   // Address
                            txtCity.Text         = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.InnerText;   // City
                            txtCounty.Text       = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText;   // County
                            txtState.Text        = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;   // State
                            mtbZIPCode.Text      = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText; // ZIP-Code
                        }
                    }
                }
    
                XmlDocument xdWaterMeters = new XmlDocument();
                string? strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";
    
                FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);
    
                if (fiWaterMeters.Exists)
                {
                    using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        xdWaterMeters.Load(fsWaterMeters);
                        XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;
    
                        foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                        {
                            txtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                                   xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                                   xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")";
                        }
                    }
                }
            }
    
            private void btnFindCustomerAccount_Click(object sender, EventArgs e)
            {
                string? strMeterNumber = null;
                XmlDocument xdCustomers = new XmlDocument();
                string? strCustomers = @"C:\Stellar Water Point\Customers.xml";
    
                FileInfo? fiCustomers = new FileInfo(strCustomers);
    
                if (fiCustomers.Exists)
                {
                    using (FileStream? fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        xdCustomers.Load(fsCustomers);
                        XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + mtbAccountNumber.Text + "']")!;
    
                        foreach (XmlNode xnCustomer in xnlCustomers)
                        {
                            strMeterNumber       = xnCustomer.NextSibling!.InnerText;   // Meter #
                            txtCustomerName.Text = xnCustomer.NextSibling.NextSibling!.InnerText + " " +
                                                   xnCustomer.NextSibling.NextSibling.NextSibling!.InnerText;   // Customer Name
                            txtAddress.Text      = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;   // Address
                            txtCity.Text         = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.InnerText;   // City
                            txtCounty.Text       = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText;   // County
                            txtState.Text        = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;   // State
                            mtbZIPCode.Text      = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText; // ZIP-Code
                        }
                    }
                }
    
                XmlDocument xdWaterMeters  = new XmlDocument();
                string?     strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";
    
                FileInfo? fiWaterMeters    = new FileInfo(strWaterMeters);
    
                if (fiWaterMeters.Exists)
                {
                    using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        xdWaterMeters.Load(fsWaterMeters);
                        XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;
    
                        foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                        {
                            txtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                                   xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                                   xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")";
                        }
                    }
                }
            }
    
            private void dtpMeterReadingEndDate_ValueChanged(object sender, EventArgs e)
            {
                TimeSpan tsDays = dtpMeterReadingEndDate.Value - dtpMeterReadingStartDate.Value;
    
                txtBillingDays.Text = tsDays.Days.ToString();
            }
    
            private void btnEvaluateWaterBill_Click(object sender, EventArgs e)
            {
                double counterStart = 0, counterEnd = 0;
    
                try
                {
                    counterStart = double.Parse(txtCounterReadingStart.Text);
                }
                catch (FormatException feCRStart)
                {
                    MessageBox.Show("There was a problem with the value of the " +
                                    "Counter Reading Start. The error produced is: " + feCRStart.Message,
                                    "Stellar Water Point", MessageBoxButtons.OK, MessageBoxIcon.Information);
                }
    
                try
                {
                    counterEnd = double.Parse(txtCounterReadingEnd.Text);
                }
                catch (FormatException feCREnd)
                {
                    MessageBox.Show("There was a problem with the value of the " +
                                    "Counter Reading End. The error produced is: " + feCREnd.Message,
                                    "Stellar Water Point", MessageBoxButtons.OK, MessageBoxIcon.Information);
                }
    
                double consumption  = counterEnd - counterStart;
                double gallons      = consumption * 748.05;
                double firstTier    = gallons * (48.00 / 10000.00);
                double secondTier   = gallons * (32.00 / 10000.00);
                double lastTier     = gallons * (20.00 / 10000.00);
                double waterCharges = firstTier + secondTier + lastTier;
                double sewerCharges = waterCharges * 28.65 / 100;
                double envCharges   = waterCharges * 0.22184;
                double totalCharges = waterCharges + sewerCharges + envCharges;
                double localTaxes   = totalCharges * 0.06148;
                double stateTaxes   = totalCharges * 0.01374;
                double amtDue       = totalCharges + localTaxes + stateTaxes;
    
                TimeSpan tsPaymentDueDate = new TimeSpan(15, 0, 0, 0);
    
                txtTotalCCF.Text              = consumption.ToString();
                txtTotalGallons.Text          = gallons.ToString("F");
                txtFirstTierConsumption.Text  = firstTier.ToString("F");
                txtSecondTierConsumption.Text = secondTier.ToString("F");
                txtLastTierConsumption.Text   = lastTier.ToString("F");
                txtWaterCharges.Text          = waterCharges.ToString("F");
                txtSewerCharges.Text          = sewerCharges.ToString("F");
                txtEnvironmentCharges.Text    = envCharges.ToString("F");
                txtTotalCharges.Text          = totalCharges.ToString("F");
                txtLocalTaxes.Text            = localTaxes.ToString("F");
                txtStateTaxes.Text            = stateTaxes.ToString("F");
                dtpPaymentDueDate.Value       = dtpMeterReadingEndDate.Value + tsPaymentDueDate;
                txtAmountDue.Text             = amtDue.ToString("F");
                dtpLatePaymentDueDate.Value   = dtpMeterReadingEndDate.Value + new TimeSpan(30, 0, 0, 0);
                txtLateAmountDue.Text         = (amtDue + 8.95).ToString("F");
            }
    
            private void btnUpdateWaterBill_Click(object sender, EventArgs e)
            {
                FileStream? fsWaterBills  = null;
                XmlDocument xdWaterBills  = new XmlDocument();
                string      strWaterBills = @"C:\Stellar Water Point\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);
                        XmlNodeList xnlWaterBills = xdWaterBills.DocumentElement!.SelectNodes("//bill-number[.='" + txtBillNumber.Text + "']")!;
                        
                        foreach (XmlNode xnWaterBill in xnlWaterBills)
                        {
                            xnWaterBill.ParentNode!.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-gallons>"            + txtTotalGallons.Text          + "</total-gallons>"           +
                                                               "<total-ccf>"                + txtTotalCCF.Text              + "</total-ccf>"               +
                                                               "<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>"     +
                                                               "<total-charges>"            + txtTotalCharges.Text          + "</total-charges>"           +
                                                               "<local-taxes>"              + txtLocalTaxes.Text            + "</local-taxes>"             +
                                                               "<state-taxes>"              + txtStateTaxes.Text            + "</state-taxes>"             +
                                                               "<amount-due>"               + txtAmountDue.Text             + "</amount-due>"              +
                                                               "<payment-due-date>"         + dtpPaymentDueDate.Value.ToShortDateString()                  + "</payment-due-date>" +
                                                               "<late-amount-due>"          + txtLateAmountDue.Text         + "</late-amount-due>"         +
                                                               "<late-payment-due-date>"    + dtpLatePaymentDueDate.Value.ToShortDateString()              + "</late-payment-due-date>";
                        }
                    }
    
                    using (fsWaterBills = new FileStream(fiWaterBills.FullName, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.ReadWrite))
                    {
                        xdWaterBills.Save(fsWaterBills);
                    }
                }
    
                Close();
            }
        }
    }

37. To create a new form, in the Solution Explorer, right-click Water Bills -> New -> Form (Windows Forms)...
38. Type Delete as the name of the form
39. Click Add
40. Make that form the same size as the Water Bill Editor form
41. Select everything on the Water Bill Editor form. Copy that selection and paste it in the new Delete form
42. Delete the Find Customer Account button
43. Complete the design of the form as follows:

    

    Control		(Name)	Text
    Button		btnDeleteWaterBill	&Update Water Bill

44. On the form, double-click the Find Water Bill button
45. Return tp the form and double-click the Delete Water Bill button
46. Return tp the form and double-click the Close button
47. Change the document as follows:

    using System.Xml;
    
    namespace StellarWaterPoint.WaterBills
    {
        public partial class Delete : Form
        {
            public Delete()
            {
                InitializeComponent();
            }
    
            private void btnFindWaterBill_Click(object sender, EventArgs e)
            {
                if (string.IsNullOrEmpty(txtBillNumber.Text))
                {
                    MessageBox.Show("You must type a bill number." +
                                    "Otherwise, the account cannot be saved.",
                                    "Stellar Water Point", MessageBoxButtons.OK);
                    return;
                }
    
                string? strMeterNumber = null;
    
                FileStream? fsWaterBills  = null;
                XmlDocument xdWaterBills  = new XmlDocument();
                string      strWaterBills = @"C:\Stellar Water Point\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);
                        XmlNodeList xnlWaterBills = xdWaterBills.DocumentElement!.SelectNodes("//bill-number[.='" + txtBillNumber.Text + "']")!;
    
                        foreach (XmlNode xnWaterBill in xnlWaterBills)
                        {
                            mtbAccountNumber.Text          = xnWaterBill.NextSibling!.InnerText;
                            dtpMeterReadingStartDate.Value = DateTime.Parse(xnWaterBill.NextSibling!.NextSibling!.InnerText);
                            dtpMeterReadingEndDate.Value   = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling!.InnerText);
                            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;
                            txtTotalGallons.Text           = xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText;
                            txtTotalCCF.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;
                            txtTotalCharges.Text           = xnWaterBill.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!.InnerText;
                            txtStateTaxes.Text             = xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                            txtAmountDue.Text              = xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                            dtpPaymentDueDate.Value        = DateTime.Parse(xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText);
                            txtLateAmountDue.Text          = xnWaterBill.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;
                            dtpLatePaymentDueDate.Value    = 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);
                        }
                    }
                }
    
                XmlDocument xdCustomers  = new XmlDocument();
                string?     strCustomers = @"C:\Stellar Water Point\Customers.xml";
    
                FileInfo?   fiCustomers  = new FileInfo(strCustomers);
    
                if (fiCustomers.Exists)
                {
                    using (FileStream? fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        xdCustomers.Load(fsCustomers);
                        XmlNodeList xnlCustomers = xdCustomers.DocumentElement!.SelectNodes("//account-number[.='" + mtbAccountNumber.Text + "']")!;
    
                        foreach (XmlNode xnCustomer in xnlCustomers)
                        {
                            strMeterNumber       = xnCustomer.NextSibling!.InnerText;   // Meter #
                            txtCustomerName.Text = xnCustomer.NextSibling.NextSibling!.InnerText + " " +
                                                   xnCustomer.NextSibling.NextSibling.NextSibling!.InnerText;   // Custome Name
                            txtAddress.Text      = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.InnerText;   // Address
                            txtCity.Text         = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.InnerText;   // City
                            txtCounty.Text       = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.InnerText;   // County
                            txtState.Text        = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText;   // State
                            mtbZIPCode.Text      = xnCustomer.NextSibling.NextSibling.NextSibling.NextSibling!.NextSibling!.NextSibling!.NextSibling!.NextSibling!.InnerText; // ZIP-Code
                        }
                    }
                }
    
                XmlDocument xdWaterMeters = new XmlDocument();
                string? strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";
    
                FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);
    
                if (fiWaterMeters.Exists)
                {
                    using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        xdWaterMeters.Load(fsWaterMeters);
                        XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + strMeterNumber + "']")!;
    
                        foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                        {
                            txtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                                   xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                                   xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")";
                        }
                    }
                }
            }
    
            private void btnDeleteWaterBill_Click(object sender, EventArgs e)
            {
                XmlDocument xdWaterMeters = new XmlDocument();
                string? strWaterMeters = @"C:\Stellar Water Point\WaterBills.xml";
    
                if (string.IsNullOrEmpty(mtbAccountNumber.Text))
                {
                    MessageBox.Show("You must type a bill number for the water bill you want to delete.",
                                    "Stellar Water Point", MessageBoxButtons.OK, MessageBoxIcon.Information);
                    return;
                }
    
                if (!File.Exists(strWaterMeters))
                {
                    MessageBox.Show("There is no file for the water bills in the system.",
                                    "Stellar Water Point",
                                    MessageBoxButtons.OK, MessageBoxIcon.Information);
                    return;
                }
    
                xdWaterMeters.Load(strWaterMeters);
    
                XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.GetElementsByTagName("bill-number");
    
                foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                {
                    if (xnWaterMeter.InnerText == txtBillNumber.Text)
                    {
                        if (MessageBox.Show("Are you sure you want to delete this water bill from the system?",
                                            "Stellar Water Point",
                                            MessageBoxButtons.YesNo, MessageBoxIcon.Question) == DialogResult.Yes)
                        {
                            xdWaterMeters.DocumentElement.RemoveChild(xnWaterMeter.ParentNode!);
                            break;
                        }
                    }
                }
    
                xdWaterMeters.Save(strWaterMeters);
    
                Close();
            }
    
            private void btnClose_Click(object sender, EventArgs e)
            {
                Close();
            }
        }
    }

Finalizing the Application

In previous sections, we created some forms for water meters and customers. Their sections included a form that shos a list of their records. We also created some forms for the water bills. Now we can provide a central form for the application. From that form, a user can navigate to the other sections of the application.

Practical Learning: Laying Out the Documents

1. In the Solution Explorer, right-click Form1.cs and click Rename
2. Change the name to WaterDistribution.cs
3. Press Enter three times to apply the name and display the form
4. In the Properties window, change the following characteristics:
   Text: Stellar Water Point
   StartPosition: CenterScreen
   MaximizeBox: False
5. Complete the design of the form as follows:

   

   Control		(Name)	Text	Font
   Button		btnProcessingWaterBill	&Water Bill Processing...	Times New Roman, 24pt, style=Bold
   Button		btnViewWaterBill	&View Water Bill...	Times New Roman, 24pt, style=Bold
   Button		btnEditWaterBill	&Edit Water Bill...	Times New Roman, 24pt, style=Bold
   Button		btnDeleteWaterBill	&Delete Water Bill...	Times New Roman, 24pt, style=Bold
   Button		btnCustomers	C&ustomers...	Times New Roman, 24pt, style=Bold
   Button		btnWaterMeters	&Water Meters...	Times New Roman, 24pt, style=Bold
   Button		btnClose	&Close	Times New Roman, 24pt, style=Bold

6. Double-click an unoccupied area of the form to generate its Load event
7. Return to the Stellar Water Point form and double-click the &Water Bill Processing button
8. Return to the Stellar Water Point form and double-click the &View Water Bill button
9. Return to the Stellar Water Point form and double-click the &Edit Water Bill button
10. Return to the Stellar Water Point form and double-click the &Delete Water Bill button
11. Return to the Stellar Water Point form and double-click the C&ustomers button
12. Return to the Stellar Water Point form and double-click the &Water Meters button
13. Return to the Stellar Water Point form and double-click the Close button
14. Change the document as follows:

    namespace StellarWaterPoint
    {
        public partial class Switchboard : Form
        {
            public Switchboard()
            {
                InitializeComponent();
            }
    
            private void Switchboard_Load(object sender, EventArgs e)
            {
                Directory.CreateDirectory(@"C:\Stellar Water Point");
            }
    
            private void btnProcessingWaterBill_Click(object sender, EventArgs e)
            {
                WaterBills.Create create = new WaterBills.Create();
    
                create.ShowDialog();
            }
    
            private void btnViewWaterBill_Click(object sender, EventArgs e)
            {
                WaterBills.Details details = new WaterBills.Details();
    
                details.ShowDialog();
            }
    
            private void btnEditWaterBill_Click(object sender, EventArgs e)
            {
                WaterBills.Editor editor = new WaterBills.Editor();
    
                editor.ShowDialog();
            }
    
            private void btnDeleteWaterBill_Click(object sender, EventArgs e)
            {
                WaterBills.Delete delete = new WaterBills.Delete();
    
                delete.ShowDialog();
            }
    
    
            private void btnWaterMeters_Click(object sender, EventArgs e)
            {
                WaterMeters.Central central = new WaterMeters.Central();
    
                central.ShowDialog();
            }
    
            private void btnCustomers_Click(object sender, EventArgs e)
            {
                Customers.Central central = new Customers.Central();
    
                central.ShowDialog();
            }
    
            private void btnClose_Click(object sender, EventArgs e)
            {
                Close();
            }
        }
    }

Testing the Application

After creating an application, you can test it. Of course, you must first execute it.

Practical Learning: Testing the Application

1. To execute, on the main menu, click Debug -> Start Without Debugging:

   

2. On the form, click Water Meters...
3. Click New Water Meter:

   

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

   Meter #	Make	Model	Meter Size
   392-44-572	Constance Technologies	TG-4822	5/8 Inches
   938-75-869	Stanford Trend	266G	1 1/2 Inches
   588-29-663	Estellano	NCF-226	3/4 Inches
   186-92-805	Lansome	2800	1 1/2 Inches
   799-28-461	Kensa Sons	K-584-L	3/4 Inches
   386-48-057	Estellano	NCF-226	3/4 Inches
   837-06-836	Lansome	7400	5/8 Inches
   207-94-835	Constance Technologies	TG-6220	5/8 Inches
   592-84-957	Kensa Sons	D-497-H	3/4 Inches
   374-06-284	Raynes Energica	i2022	3/4 Inches
   186-99-757	Kensa Sons	M-686-G	1 1/2 Inches
   630-07-055	Lansome	2800	3/4 Inches
   827-50-248	Standard Trend	428T	3/4 Inches
   470-68-850	Estellano	WRT-482	3/4 Inches
   649-33-505	Constance Technologies	BD-7000	5/8 Inches
   306-82-497	Lansome	9000	3/4 Inches

   

5. Close the Water Meters form
6. On the Stellar Water Point form, click Customers
7. On the Customers form, click New Customer Account:

   

8. Using the values in the following table, enter an account number, then enter a meter number and click Find Water Meter. Complethe the record with the other values. Then click Save Customer Account:

   Account #	Meter #	First Name	Last Name	Address	City	County	State	ZIP-Code
   9279-570-8394	799-28-461	Thomas	Stones	10252 Broward Ave #D4	Frederick	Frederick	MD	21703-6628
   2068-258-9486	186-92-805	Ericka	Dellaney	4819 East Munk Street	Whitehall	Fulton	PA	17340-2277
   4820-375-2842	392-44-572	Akhil	Koumari	748 Red Hills Rd	Roanoke		VA	24012-9726
   6003-386-3955	374-06-284	Mandiakandara	Marmoudi	539 Avalon Court	Greenwood	Sussex	DE	19950-2288
   9249-379-6848	588-29-663	Richard	Eghert	8280 Sligo North Way	Albright	Preston	WV	26519-4626
   7518-302-6895	207-94-835	Grace	Brenner	4299 Peachtree Court	Rockville	Montgomery	MD	20853-1512
   3028-502-9418	186-99-757	Spencer	Kershaw	338C Grayson Street	Gatchellville	York	PA	17352-3808
   5293-957-3395	386-48-057	Kelly	Davids	10484 Greenway Avenue	Mt Storm	Grant	WV	26739-6242
   2038-413-9680	938-75-869	Amidou	Gomah	2075 Rose Hills Avenue	Washington		DC	20004-1818
   7028-405-9381	306-82-497	Jonathan	Simmings	613 Meadowhill Road	Alonzaville	Shenandoah	VA	22664-2662
   5938-074-5293	592-84-957	Marie	Rath	582G Dunhill Avenue	Lanham	Prince Georges	MD	20706-4422
   1827-395-0203	470-68-850	Sathyavanthara	Khooni	10331 Chryswell Road	Washington		DC	20008-5050
   8027-304-6829	837-06-836	Anthony	Clarcksons	904 Augusta Drive	Blackbird	New Castle	DE	19734-2606
   6699-396-2905	649-33-505	Spencer	Reuter	2850 Burnsweak Avenue	Silver Spring	Montgomery	MD	20910-7272
   7080-583-5947	827-50-248	Sandra	Moffat	663 Sherry Wood East Street	Shimpstown	Franklin	PA	17236-1116

   

9. Close the Customers form
10. On the Stellar Water Point form, click Water Bill Processing

    

11. Fill the form with the following values:

    Water Bill #:             847384
    Account #: 	              3028-502-9418

12. Click Find Customer Account

    

13. Select and type the other values as follows Meter Reading Start Date: 10/03/2024 Meter Reading End Date: 01/06/2025 Counter Reading Start: 16 Counter Reading End: 28
14. Click Evaluate Water Bill

    

15. Click Save Water Bill
16. Follow the same steps to create records as follows:

    Water Bill #	Account #	Meter Reading Start Date	Meter Reading End Date	Counter Reading Start	Counter Reading End
    330820	7028-405-9381	10/03/2024	01/03/2025	9749	9906
    468550	7518-302-6895	10/05/2024	01/09/2025	96	114
    148274	9249-379-6848	10/05/2024	01/10/2025	260504	260555
    326384	2068-258-9486	10/08/2024	01/10/2025	104837	104851

17. Close the forms
18. Close Microsoft Visual Studio

Application

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