Introduction

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

Practical Learning: Introducing the Application

1. Start Microsoft Visual Studio
2. Create a Windows Forms App named StellarWaterPoint1

The Main Form of the Application

Our application will use a central form to access the other form. We will use the default form for that purpose. Our application will use records for water meters, customers, and water bills. Therefore, we will add some buttons for the forms related to those records.

Practical Learning: Preparing the Central Form of the Application

1. In the Solution Explorer, right-click Form1.cs and click Rename
2. Type WaterDistribution (to get WaterDistribution.cs) and press Enter
3. If necessary, click the body of the form to make sure it is selected.
   In the Properties window, change the following characteristics:
   Text: Stellar Water Point
   StartPosition: CenterScreen
   MaximizeBox: False
4. 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

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

    namespace StellarWaterPoint1
    {
        public partial class WaterDistribution : 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)
            {
                
            }
    
            private void btnViewWaterBill_Click(object sender, EventArgs e)
            {
                
            }
    
            private void btnEditWaterBill_Click(object sender, EventArgs e)
            {
                
            }
    
            private void btnDeleteWaterBill_Click(object sender, EventArgs e)
            {
                
            }
    
    
            private void btnWaterMeters_Click(object sender, EventArgs e)
            {
                
            }
    
            private void btnCustomers_Click(object sender, EventArgs e)
            {
                
            }
    
            private void btnClose_Click(object sender, EventArgs e)
            {
                Close();
            }
        }
    }

14. To execute the application and create a folder that will hold the records of this project, on the main menu, click Debug -> Start Without Debugging
15. To close the form and return to your programming environment, click the Close button

Water Meters

Introduction

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

A Sample XML File

The primary way we can preview our data is to create a sample XML and show the structure of data we are expecting.

Practical Learning: Creating a Sample XML File

1. Start a text editor such as Notepad
2. In the empty document, type the following lines:

   <?xml version="1.0" encoding="utf-8"?>
   <water-meters>
     <water-meter>
       <meter-number>111-22-333</meter-number>
       <make>Manufacturer</make>
       <model>A1000</model>
       <meter-size>1 Inch</meter-size>
     </water-meter>
     <water-meter>
       <meter-number>444-55-666</meter-number>
       <make>Company</make>
       <model>B2000</model>
       <meter-size>2 Inches</meter-size>
     </water-meter>
   </water-meters>

3. Save the file as Preview.xml in the directory that was created for the records of this project (C:\Stellar Water Point)

Displaying Water Meters

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

Practical Learning: Displaying Water Meters

1. To create a folder, in the Solution Explorer, right-click the StellarWaterPoint1 project -> Add -> New Folder
2. Type WaterMeters as the name of the folder
3. To create a form, in the Solution Explorer, right-click WaterMeters -> Add -> Form (Windows Forms)...
4. Type Central
5. Press Enter
6. In the Toolbox, click the ListView button and click the form
7. On the form, right-click the list view and click Edit Columns...
8. Create the columns as follows:

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

9. Click OK
10. 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...

11. Doubte-click an unoccupied area of the form to generate its Load event
12. Change the document as follows:

    using System.Xml;
    
    namespace StellarWaterPoint1.WaterMeters
    {
        public partial class Central : Form
        {
            public Central()
            {
                InitializeComponent();
            }
    
            private void ShowWaterMeters()
            {
                XmlDocument xdWaterMeters = new XmlDocument();
                string? strWaterMeters = @"C:\Stellar Water Point\Preview.xml";
    
                FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);
                
                using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open))
                {
                    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);
                    }
                }
            }
    
            private void Central_Load(object sender, EventArgs e)
            {
                ShowWaterMeters();
            }
        }
    }

13. Return to the code of the WaterDistribution.cs file and change the event that displays the water meters as follows:

    namespace StellarWaterPoint1
    {
        public partial class Switchboard : Form
        {
            public Switchboard()
            {
                InitializeComponent();
            }
            
            . . .
    
            private void btnWaterMeters_Click(object sender, EventArgs e)
            {
                WaterMeters.Central central = new WaterMeters.Central();
    
                central.ShowDialog();
            }
            
            . . .
        }
    }

14. To execute the application, on the main menu, click Debug -> Start Without Debugging
15. On the Central form, click the Water Meters button:

    

16. Close the forms and return to your programming environment

A Water Meter Record

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

Practical Learning: Creating a Water Meter Record

1. To create a form, in the Solution Explorer, right-click the WaterMeters folder -> Add -> Form (Windows Forms)...
2. Type Create
3. Click Add
4. Design the form as follows:

   

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

5. 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

6. Display the Central form under the WaterMeters folder of the Solution Explorer
7. On the Central form, double-click the New Water Meter button
8. Implement the event as follows:

   using System.Xml;
   
   namespace StellarWaterPoint10.WaterMeters
   {
       public partial class Central : Form
       {
           public Central()
           {
               InitializeComponent();
           }
   
           private void ShowWaterMeters()
           {
               // Create an XML Dom reference
               XmlDocument xdWaterMeters = new XmlDocument();
               // Declare a string variable to have the file that holds a list of water meters
               string? strWaterMeters = @"C:\Stellar Water Point1\WaterMeters.xml";
   
               // Create a FileInfo object that holds a reference to the file of water meters
               FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);
   
               // If you are about to display a list of water meters, first empty the list view
               lvwWaterMeters.Items.Clear();
   
               // Check whether a file for water meters was previously created.
               if (fiWaterMeters.Exists)
               {
                   // If such a file exists, create a Stream for it
                   using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                   {
                       // Store the stream of water meters into the XML Dom that was created earlier
                       xdWaterMeters.Load(fsWaterMeters);
                       // Get a list of the water meter elements from the XML Dom object
                       XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.ChildNodes;
   
                       int i = 1;
   
                       // Check each water meter
                       foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                       {
                           // Create a list view item to hold a record of a water meter
                           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);
   
                           // Pass the list view item to the list view object on the form
                           lvwWaterMeters.Items.Add(lviWaterMeter);
   
                           i++;
                       }
                   }
               }
           }
   
           private void Central_Load(object sender, EventArgs e)
           {
               // When the open opens, make an attempt to display a list of water meters.
               ShowWaterMeters();
           }
   
           private void btnNewWaterMeter_Click(object sender, EventArgs e)
           {
               // Get a reference to the form used to add a water meter
               Create wm = new();
               // Create a FileInfo object
               FileInfo? fiWaterMeters = null;
               // Create a file stream object
               FileStream? fsWaterMeters = null;
               // Create an XML Dom object
               XmlDocument xdWaterMeters = new XmlDocument();
               // Declare a string for a file to hold a list of water meters
               string? strWaterMeters = @"C:\Stellar Water Point1\WaterMeters.xml";
   
               /* Display the form used to create a water meter. 
                * If the user finishes using that form and click the OK button... */
               if (wm.ShowDialog() == DialogResult.OK)
               {
                   // Store the file of water meters into the FileInfo object that was previously created.
                   fiWaterMeters = new FileInfo(strWaterMeters);
   
                   /* Find out whether a list of water meters was previously created 
                    * and was stored in the string file declared above. */
                   if (fiWaterMeters.Exists)
                   {
                       /* If that file exists already, create a Stream object 
                        * for it with a read-only status. */
                       using (fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open,
                                                             FileAccess.Read, FileShare.Read))
                       {
                           // Pass the list of water meters to the XML Dom object created earlier
                           xdWaterMeters.Load(fsWaterMeters);
                       }
                   }
                   else
                   {
                       // If a file for water meters was not previously created, create it now...
                       using (fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Create,
                                                             FileAccess.Write, FileShare.Write))
                       {
                           // and create the root XML element for it
                           xdWaterMeters.LoadXml("<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
                                                 "<water-meters></water-meters>");
                           // Make sure you save the new file
                           xdWaterMeters.Save(fsWaterMeters);
                       }
                   }
   
                   // Now that the file exists, open it
                   using (fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.OpenOrCreate, 
                                                         FileAccess.ReadWrite, FileShare.ReadWrite))
                   {
                       // Start creating a new Water Meter XML element
                       XmlElement xeWaterMeter = xdWaterMeters.CreateElement("water-meter");
   
                       /* Use the values that the user had typed in the Create form.
                        * Use those values to create the child elements of the new water meter node.
                        * Assign the combination of child elements to the new water meter node. */
                       xeWaterMeter.InnerXml = "<meter-number>" + wm.mtbMeterNumber.Text + "</meter-number>" +
                                               "<make>" + wm.txtMake.Text + "</make>" +
                                               "<model>" + wm.txtModel.Text + "</model>" +
                                               "<meter-size>" + wm.txtMeterSize.Text + "</meter-size>";
                       // Once the XML element is ready, add/append it to the XML Dom that was previously created.
                       xdWaterMeters.DocumentElement!.AppendChild(xeWaterMeter);
                       // Once the new element has been created and add it to the file, save that file
                       xdWaterMeters.Save(fsWaterMeters);
                   }
               }
   
               /* Whenever the user has finished using the Create form, 
                * make an attempt to display the list of water meters. */
               ShowWaterMeters();
           }
       }
   }

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

    

12. 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	Fansa Sun	A-BBB-C	1/2 Inch
    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

    

13. Close the forms and return to your programming environment

Water Meter Details

Once a database exists, sometimes a use mmay want to check the values of a water meter record. To support this, we will add an appropriate form to our application.

Practical Learning: Creating a Water Meter Record

1. To create a form, in the Solution Explorer, right-click WaterMeters -> Add -> Form (Windows Forms)...
2. Type Details
3. Press Enter
4. Resize the Editor form to have the same size as the Create form
5. Copy everything from the Create form and paste it in the Editor form
6. Delete the bottom two buttons and add a new button
7. Change the design of the form as follows:

   

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

8. On the form, double-click the Find button
9. Return to the form and double-click the Close button
10. Change the document as follows:

    using System.Xml;
    
    namespace StellarWaterPoint10.WaterMeters
    {
        public partial class Details : Form
        {
            public Details()
            {
                InitializeComponent();
            }
    
            private void btnFindWateMeter_Click(object sender, EventArgs e)
            {
                /* If the user clicks the Find button, 
                 * make sure there is a meter number in the top text box. */
                if (string.IsNullOrEmpty(mtbMeterNumber.Text))
                {
                    /* If the user didn't type a meter number, 
                     * display a message box to inform the user. */
                    MessageBox.Show("You must type a meter number and then click the Find button.",
                                    "Stellar Water Point", MessageBoxButtons.OK, MessageBoxIcon.Information);
                    // If the user didn't type a meter number but clicked Find, don't do anything
                    return;
                }
    
                // We will need a reference to an XML Dom object as an XmlDocument variable
                XmlDocument xdWaterMeters = new XmlDocument();
                // This is the name and path of the file that holds the records of water meters
                string? strWaterMeters = @"C:\Stellar Water Point1\WaterMeters.xml";
                // We will process the file of water meters using a FileInfo object
                FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);
    
                // We need to find out whether a file for water meters was previously created.
                if (fiWaterMeters.Exists)
                {
                    // If that file exists, create a stream of it. Open that file with a read-only status
                    using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        // Get the list of water meter records and put those records in the XML Dom object created earlier.
                        xdWaterMeters.Load(fsWaterMeters);
                        /* Use XPath to locate the water meter that has 
                         * the same meter number as the one in the Meter # text box.
                         * Store the water meter in an XmlNodeList variable. */
                        XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + mtbMeterNumber.Text + "']")!;
    
                        /* If there is a water meter in the database with 
                         * the number that the user typed, locate that water meter 
                         * and display each of its values in the appropriate text box. */
                        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();
            }
        }
    }

11. Display the Central form of the WaterMeters folder
12. Double-click the View Water Meter button
13. Change the document as follows:

    using System.Xml;
    
    namespace StellarWaterPoint1.WaterMeters
    {
        public partial class Central : Form
        {
            public Central()
            {
                InitializeComponent();
            }
    
            private void ShowWaterMeters()
            {
                . . .
            }
    
            private void Central_Load(object sender, EventArgs e)
            {
                // When the open opens, make an attempt to display a list of water meters.
                ShowWaterMeters();
            }
    
            private void btnNewWaterMeter_Click(object sender, EventArgs e)
            {
                . . .
            }
    
            private void btnViewWaterMeter_Click(object sender, EventArgs e)
            {
                /* Get a reference to the dialog box that is used 
                 * to view information about a water meter. */
                Details view = new();
                // Display that dialog box
                view.ShowDialog();
    
                // After using the dialog box, make an attempt to display the list of water meters.
                ShowWaterMeters();
            }
        }
    }

14. To execute the application, on the main menu, click Debug -> Start Without Debugging
15. On the Water Distribution form, click the Water Meters button
16. On the Central form of water meters, click the View Water Meter button:

    

17. In the Meter # text, type 186-99-757
18. Click the Find button:

    

19. Close the forms and return to your programming environment

Updating a Water Meter Details

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

Practical Learning: Updating a Water Meter

1. To create a form, in the Solution Explorer, right-click WaterMeters -> Add -> Form (Windows Forms)...
2. Type Editor
3. Press Enter
4. Resize the Editor form to have the same size as the Details form
5. Copy everything from the Details form and paste it in the Editor form
6. Change the design of the form as follows:

   

   Control		(Name)	Text
   Button		btnUpdateWateMeter	&Update Water Meter

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

   using System.Xml;
   
   namespace StellarWaterPoint1.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;
                       }
                   }
               }
           }
       }
   }

9. Return to the form and double-click the Update Water Meter button
10. Change the document as follows:

    using System.Xml;
    
    namespace StellarWaterPoint1.WaterMeters
    {
        public partial class Editor : Form
        {
            public Editor()
            {
                InitializeComponent();
            }
    
            . . .
    
            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();
            }
        }
    }

11. Return to the form and double-click the Close button
12. Change the document as follows:

    using System.Xml;
    
    namespace StellarWaterPoint10.WaterMeters
    {
        public partial class Editor : Form
        {
            public Editor()
            {
                InitializeComponent();
            }
    
            private void btnFindWateMeter_Click(object sender, EventArgs e)
            {
                /* If the user clicks the Find button, 
                 * make sure there is a meter number in the top text box. */
                if (string.IsNullOrEmpty(mtbMeterNumber.Text))
                {
                    /* If the user didn't type a meter number, 
                     * display a message box to inform the user. */
                    MessageBox.Show("You must type a meter number and then click the Find button.",
                                    "Stellar Water Point", MessageBoxButtons.OK, MessageBoxIcon.Information);
                    // If the user didn't type a meter number but clicked Find, don't do anything
                    return;
                }
    
                // We will need a reference to an XML Dom object as an XmlDocument variable
                XmlDocument xdWaterMeters = new XmlDocument();
                // This is the name and path of the file that holds the records of water meters
                string? strWaterMeters = @"C:\Stellar Water Point1\WaterMeters.xml";
                // We will process the file of water meters using a FileInfo object
                FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);
    
                // We need to find out whether a file for water meters was previously created.
                if (fiWaterMeters.Exists)
                {
                    // If that file exists, create a stream of it. Open that file with a read-only status
                    using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        /* Get the list of water meter records 
                         * and put those records in the XML Dom object created earlier. */
                        xdWaterMeters.Load(fsWaterMeters);
                        /* Use XPath to locate the water meter that has 
                         * the same meter number as the one in the Meter # text box.
                         * Store the water meter in an XmlNodeList variable. */
                        XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + mtbMeterNumber.Text + "']")!;
    
                        /* If there is a water meter in the database with 
                         * the number that the user typed, locate that water meter 
                         * and display each of its values in the appropriate text box. */
                        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)
            {
                // We will need a reference to an XML Dom object as an XmlDocument variable
                XmlDocument xdWaterMeters = new();
                // This is the name and path of the file that holds the records of water meters
                string? strWaterMeters = @"C:\Stellar Water Point1\WaterMeters.xml";
                // We will process the file of water meters using a FileInfo object
                FileInfo? fiWaterMeters = new(strWaterMeters);
    
                // We need to find out whether a file for water meters was previously created.
                if (fiWaterMeters.Exists)
                {
                    // If that file exists, create a stream of it. Open that file with a read-only status
                    using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        /* Get the list of water meter records 
                         * and put those records in the XML Dom object created earlier. */
                        xdWaterMeters.Load(fsWaterMeters);
                        /* Use XPath to locate the water meter that has 
                         * the same meter number as the one in the Meter # text box.
                         * Store the water meter in an XmlNodeList variable. */
                        XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + mtbMeterNumber.Text + "']")!;
    
                        // Check each record of the water meters.
                        foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                        {
                            /* If you find a record whose water meter is 
                             * the same as the meter number that the user typed,
                             * change the values of the Make, the Model, 
                             * and the Meter Size based on the values 
                             * the user typed in the corresponding text boxes. */
                            xnWaterMeter.ParentNode!.InnerXml = "<meter-number>" + mtbMeterNumber.Text + "</meter-number>" +
                                                                "<make>" + txtMake.Text + "</make>" +
                                                                "<model>" + txtModel.Text + "</model>" +
                                                                "<meter-size>" + txtMeterSize.Text + "</meter-size>";
                        }
                    }
    
                    /* Now that a water meter has been changed/update 
                     * (and the file of water meters has changed), save the new version of the file. */
                    using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.ReadWrite))
                    {
                        xdWaterMeters.Save(fsWaterMeters);
                    }
                }
    
                /* If the user has updated a record, we will assume that, 
                 * in most cases (such as usually in real life), 
                 * a user updates one record and moves to other activities.
                 * For this record, after the user has updated a record, 
                 * we will clode the form. */
                Close();
            }
    
            private void btnClose_Click(object sender, EventArgs e)
            {
                Close();
            }
        }
    }

13. Display the Central form of the WaterMeters folder
14. Double-click the Update Water Meter button
15. Change the document as follows:

    using System.Xml;
    
    namespace StellarWaterPoint1.WaterMeters
    {
        public partial class Central : Form
        {
            public Central()
            {
                InitializeComponent();
            }
    
            private void ShowWaterMeters()
            {
                . . .
            }
    
            private void Central_Load(object sender, EventArgs e)
            {
                // When the open opens, make an attempt to display a list of water meters.
                ShowWaterMeters();
            }
    
            private void btnNewWaterMeter_Click(object sender, EventArgs e)
            {
                . . .
            }
    
            private void btnViewWaterMeter_Click(object sender, EventArgs e)
            {
                . . .
            }
    
            private void btnEditWaterMeter_Click(object sender, EventArgs e)
            {
                /* Get a reference to the dialog box that is used 
                 * to update the details of a water meter. */
                Editor editor = new();
                // Display that dialog box
                editor.ShowDialog();
    
                // After using the dialog box, make an attempt to display the list of water meters.
                ShowWaterMeters();
            }
        }
    }

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

    

19. In the Meter # text, type 186-99-757
20. Click the Find button:

    

21. Change the values as follows:

    Make:	Kensa Sons
    Model:	M-686-G
    Meter Size:	1 1/2 Inches

    :

    

22. Click the Update button:

    

23. Close the forms and return to your programming environment

Removing a Water Meter from the Database

If a record is not necessary anymore on a database, the user may want to remove it. To assist the user with this operation, we will create a form withe necessary buttons.

Practical Learning: Deleting a Water Meter Record

1. To create a form, in the Solution Explorer, right-click WaterMeters -> Add -> Form(Windows Forms)...
2. Type Delete
3. Press Enter
4. Resize the Editor form to have the same size as the Editor form
5. Copy everything from the Editor form and paste it in the Delete form
6. Change the bottom button as follows:

   

   Control		(Name)	Text
   Button		btnDeleteWateMeter	&Delete Water Meter

7. On the form, double-click the Find button
8. Change the document as tollows:

   using System.Xml;
   
   namespace StellarWaterPoint1.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;
                       }
                   }
               }
           }
       }
   }

9. Return to the form and double-click the Delete Water Meter button
10. Change the document as tollows:

    using System.Xml;
    
    namespace StellarWaterPoint1.WaterMeters
    {
        public partial class Delete : Form
        {
            public Delete()
            {
                InitializeComponent();
            }
    
            . . .
    
            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();
            }
        }
    }

11. Return to the form and double-click the Close button
12. Change the document as tollows:

    using System.Xml;
    
    namespace StellarWaterPoint10.WaterMeters
    {
        public partial class Delete : Form
        {
            public Delete()
            {
                InitializeComponent();
            }
    
            private void btnFindWateMeter_Click(object sender, EventArgs e)
            {
                /* If the user clicks the Find button, 
                 * make sure there is a meter number in the top text box. */
                if (string.IsNullOrEmpty(mtbMeterNumber.Text))
                {
                    /* If the user didn't type a meter number, 
                     * display a message box to inform the user. */
                    MessageBox.Show("You must type a meter number and then click the Find button.",
                                    "Stellar Water Point", MessageBoxButtons.OK, MessageBoxIcon.Information);
                    // If the user didn't type a meter number but clicked Find, don't do anything
                    return;
                }
    
                // We will need a reference to an XML Dom object as an XmlDocument variable
                XmlDocument xdWaterMeters = new XmlDocument();
                // This is the name and path of the file that holds the records of water meters
                string? strWaterMeters = @"C:\Stellar Water Point1\WaterMeters.xml";
                // We will process the file of water meters using a FileInfo object
                FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);
    
                // We need to find out whether a file for water meters was previously created.
                if (fiWaterMeters.Exists)
                {
                    // If that file exists, create a stream of it. Open that file with a read-only status
                    using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        /* Get the list of water meter records 
                         * and put those records in the XML Dom object created earlier. */
                        xdWaterMeters.Load(fsWaterMeters);
                        /* Use XPath to locate the water meter that has 
                         * the same meter number as the one in the Meter # text box.
                         * Store the water meter in an XmlNodeList variable. */
                        XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + mtbMeterNumber.Text + "']")!;
    
                        /* If there is a water meter in the database with 
                         * the number that the user typed, locate that water meter 
                         * and display each of its values in the appropriate text box. */
                        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)
            {
                /* If the user clicks the Delete button, make sure that 
                 * the right text box contains a meter number */
                if (string.IsNullOrEmpty(mtbMeterNumber.Text))
                {
                    // If the user didn't provide a meter number, display a message box ...
                    MessageBox.Show("You must type a water meter number if you want to delete one.",
                                    "Stellar Water Point", MessageBoxButtons.OK, MessageBoxIcon.Information);
                    // .. and stop the operation.
                    return;
                }
    
                // Create an XML Dom object
                XmlDocument xdWaterMeters = new XmlDocument();
                /* Get the file that holds a list of water meters
                 * and assign that file to a string variable. */
                string? strWaterMeters = @"C:\Stellar Water Point1\WaterMeters.xml";
    
                /* If the user provided a meter number and clicked the Find button,
                 * check whether a file for water meters was previously created. */
                if (!File.Exists(strWaterMeters))
                {
                    // If a file for water meters was not created already, display a message box...
                    MessageBox.Show("There is no file for the water meters in the system.",
                                    "Stellar Water Point",
                                    MessageBoxButtons.OK, MessageBoxIcon.Information);
                    // .. and stop the operation.
                    return;
                }
    
                /* Since a file of water meters exists, open it.
                 * Store the list of water meters in the XML Dom object that was previously created. */
                xdWaterMeters.Load(strWaterMeters);
    
                /* From the list of XML elements, get a list of elements based one named meter-number. */
                XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.GetElementsByTagName("meter-number");
    
                // Visit each XML node from the list
                foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                {
                    /* When you get to an element, check whether its meter number is 
                     * the same number the user had typed. */
                    if (xnWaterMeter.InnerText == mtbMeterNumber.Text)
                    {
                        /* If you find that meter number, enquire from 
                         * the user if the water meter must be deleted. 
                         * To get that information, display a message box with a Yes and a No buttons. */
                        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)
                        {
                            // If the user had clicked Yes, delete the water meter.
                            xdWaterMeters.DocumentElement.RemoveChild(xnWaterMeter.ParentNode!);
                            break;
                        }
                    }
                }
    
                // Since the list of water meters has been changed, save its new version
                xdWaterMeters.Save(strWaterMeters);
    
                /* After the deletion operation, close the dialog box and
                 * return to the Central form of water meters. */
                Close();
            }
    
            private void btnClose_Click(object sender, EventArgs e)
            {
                Close();
            }
        }
    }

13. Display the Central form of the WaterMeters folder
14. Double-click the Delete Water Meter button
15. Return to the Central form of the water meters and double-click the Delete Water Meter button
16. Change the document as follows:

    using System.Xml;
    
    namespace StellarWaterPoint10.WaterMeters
    {
        public partial class Central : Form
        {
            public Central()
            {
                InitializeComponent();
            }
    
            private void ShowWaterMeters()
            {
                // Create an XML Dom reference
                XmlDocument xdWaterMeters = new XmlDocument();
                // Declare a string variable to have the file that holds a list of water meters
                string? strWaterMeters = @"C:\Stellar Water Point1\WaterMeters.xml";
    
                // Create a FileInfo object that holds a reference to the file of water meters
                FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);
    
                // If you are about to display a list of water meters, first empty the list view
                lvwWaterMeters.Items.Clear();
    
                // Check whether a file for water meters was previously created.
                if (fiWaterMeters.Exists)
                {
                    // If such a file exists, create a Stream for it
                    using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        // Store the stream of water meters into the XML Dom that was created earlier
                        xdWaterMeters.Load(fsWaterMeters);
                        // Get a list of the water meter elements from the XML Dom object
                        XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.ChildNodes;
    
                        int i = 1;
    
                        // Check each water meter
                        foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                        {
                            // Create a list view item to hold a record of a water meter
                            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);
    
                            // Pass the list view item to the list view object on the form
                            lvwWaterMeters.Items.Add(lviWaterMeter);
    
                            i++;
                        }
                    }
                }
            }
    
            private void Central_Load(object sender, EventArgs e)
            {
                // When the open opens, make an attempt to display a list of water meters.
                ShowWaterMeters();
            }
    
            private void btnNewWaterMeter_Click(object sender, EventArgs e)
            {
                // Get a reference to the form used to add a water meter
                Create wm = new();
                // Create a FileInfo object
                FileInfo? fiWaterMeters = null;
                // Create a file stream object
                FileStream? fsWaterMeters = null;
                // Create an XML Dom object
                XmlDocument xdWaterMeters = new XmlDocument();
                // Declare a string for a file to hold a list of water meters
                string? strWaterMeters = @"C:\Stellar Water Point1\WaterMeters.xml";
    
                /* Display the form used to create a water meter. 
                 * If the user finishes using that form and click the OK button... */
                if (wm.ShowDialog() == DialogResult.OK)
                {
                    // Store the file of water meters into the FileInfo object that was previously created.
                    fiWaterMeters = new FileInfo(strWaterMeters);
    
                    /* Find out whether a list of water meters was previously created 
                     * and was stored in the string file declared above. */
                    if (fiWaterMeters.Exists)
                    {
                        /* If that file exists already, create a Stream object 
                         * for it with a read-only status. */
                        using (fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open,
                                                              FileAccess.Read, FileShare.Read))
                        {
                            // Pass the list of water meters to the XML Dom object created earlier
                            xdWaterMeters.Load(fsWaterMeters);
                        }
                    }
                    else
                    {
                        // If a file for water meters was not previously created, create it now...
                        using (fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Create,
                                                              FileAccess.Write, FileShare.Write))
                        {
                            // and create the root XML element for it
                            xdWaterMeters.LoadXml("<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
                                                  "<water-meters></water-meters>");
                            // Make sure you save the new file
                            xdWaterMeters.Save(fsWaterMeters);
                        }
                    }
    
                    // Now that the file exists, open it
                    using (fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.OpenOrCreate,
                                                          FileAccess.ReadWrite, FileShare.ReadWrite))
                    {
                        // Start creating a new Water Meter XML element
                        XmlElement xeWaterMeter = xdWaterMeters.CreateElement("water-meter");
    
                        /* Use the values that the user had typed in the Create form.
                         * Use those values to create the child elements of the new water meter node.
                         * Assign the combination of child elements to the new water meter node. */
                        xeWaterMeter.InnerXml = "<meter-number>" + wm.mtbMeterNumber.Text + "</meter-number>" +
                                                "<make>" + wm.txtMake.Text + "</make>" +
                                                "<model>" + wm.txtModel.Text + "</model>" +
                                                "<meter-size>" + wm.txtMeterSize.Text + "</meter-size>";
                        // Once the XML element is ready, add/append it to the XML Dom that was previously created.
                        xdWaterMeters.DocumentElement!.AppendChild(xeWaterMeter);
                        // Once the new element has been created and add it to the file, save that file
                        xdWaterMeters.Save(fsWaterMeters);
                    }
                }
    
                /* Whenever the user has finished using the Create form, 
                 * make an attempt to display the list of water meters. */
                ShowWaterMeters();
            }
    
            private void btnViewWaterMeter_Click(object sender, EventArgs e)
            {
                /* Get a reference to the dialog box that is used 
                 * to view information about a water meter. */
                Details view = new();
                // Display that dialog box
                view.ShowDialog();
    
                // After using the dialog box, make an attempt to display the list of water meters.
                ShowWaterMeters();
            }
    
            private void btnEditWaterMeter_Click(object sender, EventArgs e)
            {
                /* Get a reference to the dialog box that is used 
                 * to update the details of a water meter. */
                Editor editor = new();
                // Display that dialog box
                editor.ShowDialog();
    
                // After using the dialog box, make an attempt to display the list of water meters.
                ShowWaterMeters();
            }
    
            private void btnDeleteWateMeter_Click(object sender, EventArgs e)
            {
                Delete del = new Delete();
                del.ShowDialog();
    
                ShowWaterMeters();
            }
    
            private void btnClose_Click(object sender, EventArgs e)
            {
                Close();
            }
        }
    }

17. To execute the application, on the main menu, click Debug -> Start Without Debugging
18. On the Central form, click the Water Meters button:

    

19. Click the Delete Water Meter button:

    

20. In the Meter # text, type 630-07-055
21. Click the Find button:

    

22. Click the Delete button:

    

23. On the message box, click Yes:

    

24. Close the forms and return to your programming environment

Customers

Introduction

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

Customers Accounts

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

Practical Learning: Displaying Customers Accounts

1. To create a folder, 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, in the Solution Explorer, right-click Models -> Add -> Form (Windows Forms)...
4. Type Central
5. Click Add
6. In the Toolbox, click the ListView button and click the form
7. On the form, right-click the list view and click Edit Columns...
8. 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

9. Click OK
10. 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		btnCreateCustomerAccount	&Create 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

11. Doubte-click an unoccupied area of the form to generate its Load event
12. Change the document as follows:

    using System.Xml;
    
    namespace StellarWaterPoint1.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();
            }       
        }
    }

13. Display the code of the WaterDistribution.cs file and change the event that displays the customers as follows:

    namespace StellarWaterPoint1
    {
        public partial class WaterDistribution : 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)
            {
                
            }
    
            private void btnViewWaterBill_Click(object sender, EventArgs e)
            {
                
            }
    
            private void btnEditWaterBill_Click(object sender, EventArgs e)
            {
                
            }
    
            private void btnDeleteWaterBill_Click(object sender, EventArgs e)
            {
                
            }
    
            private void btnCustomers_Click(object sender, EventArgs e)
            {
                Customers.Central central = new Customers.Central();
    
                central.ShowDialog();
            }
    
            private void btnWaterMeters_Click(object sender, EventArgs e)
            {
                WaterMeters.Central central = new WaterMeters.Central();
    
                central.ShowDialog();
            }
    
            private void btnClose_Click(object sender, EventArgs e)
            {
                Close();
            }
        }
    }

A Customer's Account

As mentioned already, our application will use a database that contains a list of customers. This means that a customer must have an account. We will create a form to let the user create an account. One important detail is that a customer must have a water meter. Therefore, each customer account must have an associated water meter. To set this up, on the form used to create a customer's account, we will add a text box that allows a user to specify and validate a water meter.

Practical Learning: Creating a Customer Account

1. In the Solution Explorer, right-click the Customers folder -> Add -> Form (Windows Forms)...
2. Type Create as the name of the file
3. Click Add
4. 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

5. 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

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

   using System.Xml;
   
   namespace StellarWaterPoint1.Customers
   {
       public partial class Create : Form
       {
           public Create()
           {
               InitializeComponent();
           }
   
           private void btnFindWaterMeter_Click(object sender, EventArgs e)
           {
               // Create an XML Dom object
               XmlDocument xdWaterMeters = new XmlDocument();
               // Declare a string variable and assign the file of water meters to it
               string? strWaterMeters = @"C:\Stellar Water Point\WaterMeters.xml";
               // Create a FileInfo object to manage the file that has the water meters
               FileInfo? fiWaterMeters = new FileInfo(strWaterMeters);
   
               // Find out whether a file for water meters exists already
               if (fiWaterMeters.Exists)
               {
                   // If a file for water meters exists already, create a Stream object for it
                   using (FileStream? fsWaterMeters = new FileStream(fiWaterMeters.FullName, FileMode.Open,
                                                                     FileAccess.Read, FileShare.Read))
                   {
                       /* From the file of water meters, store the list of water meters 
                        * in the XML Dom that was previously created. */
                       xdWaterMeters.Load(fsWaterMeters);
   
                       /* Check the list of water meters. 
                        * Find a water meter that has the same name as the meter number that the user typed. */
                       XmlNodeList xnlWaterMeters = xdWaterMeters.DocumentElement!.SelectNodes("//meter-number[.='" + mtbMeterNumber.Text + "']")!;
   
                       // If such a water meter exists...
                       foreach (XmlNode xnWaterMeter in xnlWaterMeters)
                       {
                           // ... store its details in the meter details text box.
                           txtMeterDetails.Text = xnWaterMeter.NextSibling!.InnerText + " " +
                                                  xnWaterMeter.NextSibling.NextSibling!.InnerText + " (Meter Size: " +
                                                  xnWaterMeter.NextSibling.NextSibling.NextSibling!.InnerText + ")";
                       }
                   }
               }
           }
       }
   }

8. Display the Central form of the Customers folder
9. Double-click the Create Customer Account button
10. Change the document as follows:

    using System.Xml;
    
    namespace StellarWaterPoint10.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 Point1\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)
            {
                // When the form opens, try displaying the list of customers
                ShowCustomers();
            }
    
            private void btnCreateCustomerAccount_Click(object sender, EventArgs e)
            {
                Create create = new Create();
    
                if (create.ShowDialog() == DialogResult.OK)
                {
                    /* Make sure the user provides an account number for the new account. 
                     * If not, don't create the account. */
                    if (string.IsNullOrEmpty(create.mtbAccountNumber.Text))
                    {
                        MessageBox.Show("You must provide an account number for the new customer. " +
                                        "Otherwise, the account cannot be created.",
                                        "Stellar Water Point",
                                        MessageBoxButtons.OK, MessageBoxIcon.Information);
    
                        return;
                    }
    
                    /* If the meter details text box is empty, it means the user didn't enter
                     * a meter number, in which case there is no water meter associated 
                     * with the account. The account cannot be created. */
                    if (string.IsNullOrEmpty(create.txtMeterDetails.Text))
                    {
                        MessageBox.Show("You must enter a water meter to associate with a new customer's account.",
                                        "Stellar Water Point",
                                        MessageBoxButtons.OK, MessageBoxIcon.Information);
                        
                        return;
                    }
                    
                    // Create a FileInfo object that will be used to manage a file
                    FileInfo? fiCustomers = null;
                    // Start a Stream object that will be used to manage a file
                    FileStream? fsCustomers = null;
                    // Create an XML Dom
                    XmlDocument xdCustomers = new XmlDocument();
                    // Declare a string variable for the file that contains a list of customers
                    string? strCustomers = @"C:\Stellar Water Point1\Customers.xml";
                    
                    // Pass the file of customers to the FileInfo object that was started
                    fiCustomers = new FileInfo(strCustomers);
    
                    // Find out whether that file was already created
                    if (fiCustomers.Exists)
                    {
                        /* If that file was already created, open it through 
                         * the Stream object that was previously initiated. */
                        using (fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Open,
                                                            FileAccess.Read, FileShare.Read))
                        {
                            // Pass the Stream object to the XML Dom that was previously created.
                            xdCustomers.Load(fsCustomers);
                        }
                    }
                    else
                    {
                        /* If the file of customers was not created already, start by 
                         * initializing the Stream object that was previously initiated. */
                        using (fsCustomers = new FileStream(fiCustomers.FullName, FileMode.Create, FileAccess.Write, FileShare.Write))
                        {
                            // Create a root to start the XML file
                            xdCustomers.LoadXml("<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
                                                "<customers></customers>");
                            // Once the file has been started, save it
                            xdCustomers.Save(fsCustomers);
                        }
                    }
    
                    // Now that we have an XML file for customers, open it
                    using (fsCustomers = new FileStream(fiCustomers.FullName, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.ReadWrite))
                    {
                        /* We want to create an XML element to be added to the XML file.
                         * To start, create an XML element named "customer". */
                        XmlElement xeCustomer = xdCustomers.CreateElement("customer");
    
                        // Create/Format the child nodes of the "customer" element
                        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();
            }
        }
    }

11. To execute the application, on the main menu, click Debug -> Start Without Debugging
12. On the Water Distribution form, click the Customers button
13. On the Central form of the customers, click the Create Customer Account button:

    

14. In the account # text box, type 9279-570-8394
15. In the meter # text box, type 799-28-461
16. Click the Find water meter button
17. Using the values in the following table, enter an account number, then enter a meter number and click Find Water Meter. Complete 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	207-94-835	Mendia	Mahmoud	53 Avalon Crt	Greener	Essex	DW	19250-2008
    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

    

18. Close the forms and return to your programming environment

namespace StellarWaterPoint1
{
    public partial class WaterDistribution : 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 btnCustomers_Click(object sender, EventArgs e)
        {
            Customers.Central central = new Customers.Central();

            central.ShowDialog();
        }

        private void btnClose_Click(object sender, EventArgs e)
        {
            Close();
        }
    }
}

1. Type Customers as the name of the folder
2. To create a form, on the main menu, click Customers -> Add ->
3. Return to the form and double-click the Edit Water Meter button
4. Return to the form and double-click the Delete Water Meter button
5. Return to the form and double-click the Close button
6. Change the document as follows:

   
           private void btnDeleteWaterMeter_Click(object sender, EventArgs e)
           {
               Delete delete = new();
   
               delete.ShowDialog();
   
               ShowWaterMeters();
           }
   
           private void btnClose_Click(object sender, EventArgs e)
           {
               Close();
           }
       }
   }

Practical Learning: Preparing Customers Accounts

1. To create a form, in the Solution Explorer, right-click Customers -> Add -> Form (Windows Forms)...
2. Type Details
3. Press Enter
4. Resize the Editor form to have the same size as the Create form
5. Copy everything from the Create form and paste it in the Editor form
6. Delete the bottom two buttons and add a new button
7. Change the design of the form as follows:

   

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

8. 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

9. On the form, double-click the Find Customer Account
10. Return to the form and double-click the Close button
11. Change the document as follows:

    using System.Xml;
    
    namespace StellarWaterPoint1.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 + ")";
                        }
                    }
                }
            }
        }
    }

12. To create a form, in the Solution Explorer, right-click Customers -> Add -> Form (Windows Forms)...
13. Type Editor
14. Press Enter
15. Resize the Editor form to have the same size as the Create form
16. Copy everything from the Create form and paste it in the Editor form
17. 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

18. 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

19. On the form, double-click the Find Customer Account
20. Return to the form and double-click the Find Water Meter button
21. Return to the form and double-click the Update Water Meter button
22. Change the document as tollows:

    using System.Xml;
    
    namespace StellarWaterPoint1.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();
            }
        }
    }

23. To create a form, in the Solution Explorer, right-click Customers -> Add -> Form (Windows Forms)...
24. Type Delete
25. Press Enter
26. Resize the Editor form to have the same size as the Editor form
27. Copy everything from the Editor form and paste it in the Delete form
28. Delete the Find Water Meter button and change the bottom button as follows:

    

    Control		(Name)	Text
    Button		btnDeleteCustomerAccount	&Delete Customer Account

29. 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

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

    using System.Xml;
    
    namespace StellarWaterPoint1.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();
            }
        }
    }

33. Return to the form and double-click the New Customer Account button
34. Return to the form and double-click the View Customer Account button
35. Return to the form and double-click the Edit Customer Account button
36. Return to the form and double-click the Delete Customer Account button
37. Return to the form and double-click the Close button
38. Change the document as follows:

    
            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 StellarWaterPoint1.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 StellarWaterPoint1.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 StellarWaterPoint1.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 StellarWaterPoint1.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();
            }
        }
    }

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. Close the Water Meters form
4. On the Stellar Water Point form, click Water Bill Processing

   

5. Fill the form with the following values:

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

6. Click Find Customer Account

   

7. 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
8. Click Evaluate Water Bill

   

9. Click Save Water Bill
10. 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

11. Close the forms
12. Close Microsoft Visual Studio

Application

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