Lesson 09: Operations on XML Elements

	Operations on XML Elements

Fundamental Operations

Introduction

So far, to create an XML element, we were directly typing in a file. When such a file had been created and saved, it was ready to be processed. Here is an example of a file named videos.xml:

<?xml version="1.0" encoding="utf-8" ?>
<videos>
  <title>The Distinguished Gentleman</title>
</videos>

In some applications, you will want the user to provide you with the necessary value(s) to create an element. Fortunately, the XmlDocument, the XmlNode, and the XmlElement classes provide all the necessary properties and methods to perform the routine operations of an XML file, an element, or a node. The operations include locating a node, adding a new element, or deleting a node.

Before performing an operation, you will usually need to decide in what section of the file you want the action to be applied. As it happens, you have the root node, a particular node inside the document, parent of a node, the sibling of a node, etc. To get to a node, you will usually first get a reference to its XmlElement. To do this, you can declare an XmlElement variable and initialize it with that reference.

Practical Learning: Introducing operations on XML Elements

Start Microsoft Visual C# and create a Console Application named SolasPropertyRental1
To add a new form to the application, in the Solution Explorer, right-click SolasPropertyRental1 -> Add -> Windows Form...
Set the Name to Tenants and click Add
From the Toolbox, add a ListView to the form

While the new list view is still selected, in the Properties window, click the ellipsis button of the Columns field and create the columns as follows:

(Name)	Text	TextAlign	Width
colAccountNumber	Account #		65
colFullName	Full Name		120
colMaritalStatus	Marital Status		85
colPhoneNumber	Phone #	Center	85

Design the form as follows:

Control	Text	Name	Other Properties
ListView		lvwTenants	Anchor: Top, Bottom, Left, Right FullRowSelect: True GridLines: True View: Details
Button	New Tenant...	btnNewTenant	Anchor: Bottom, Right
Button	Close	btnClose	Anchor: Bottom, Right

Double-click an unoccupied area of the Tenants form

Implement the Load event as follows:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO;
using System.Xml;

namespace SolasPropertyRental1
{
    public partial class Tenants : Form
    {
        public Tenants()
        {
            InitializeComponent();
        }

        void ShowTenants()
        {
            string Filename = @"C:\Solas Property Rental\tenants.xml";
            XmlDocument docTenants = new XmlDocument();

            if (File.Exists(Filename))
            {
                lvwTenants.Items.Clear();

                docTenants.Load(Filename);
                XmlElement elmTenant = docTenants.DocumentElement;
                XmlNodeList lstTenants = elmTenant.ChildNodes;

                foreach (XmlNode node in lstTenants)
                {
                    ListViewItem lviTenant = new ListViewItem(node.FirstChild.InnerText); // Account Number

                    lviTenant.SubItems.Add(node.FirstChild.NextSibling.InnerText); // Full Name
                    lviTenant.SubItems.Add(node.FirstChild.NextSibling.NextSibling.InnerText); // Phone Number
                    lviTenant.SubItems.Add(node.FirstChild.NextSibling.NextSibling.NextSibling.InnerText); // Marital Status
                    lvwTenants.Items.Add(lviTenant);
                }
            }
        }

        private void Tenants_Load(object sender, EventArgs e)
        {
            ShowTenants();
        }
    }
}

To add another form to the application, in the Solution Explorer, right- click SolasPropertyRental1 -> Add -> Windows Form...
Set the Name to TenantEditor and click Add

Design the form as follows:

Control	Text	Name	Properties
Label	&Account #:
MaskedTextBox		txtAccountNumber	Mask: 00-00-00 Modifiers: public
Label	&Full Name:
TextBox		txtFullName	Modifiers: public
Label	Marital Status:
ComboBox		txtMaritalStatus	Modifiers: public Items: Single Widow Married Divorced Separated
Label	&Phone #:
MaskedTextBox		txtPhoneNumber	Mask: (999) 000-0000 Modifiers: public
Button	OK	btnOK	DialogResult: OK
Button	Cancel	btnCancel	DialogResult: Cancel
Form			AcceptButton: btnOK CancelButton: btnCancel FormBorderStyle: FixedDialog MaximizeBox: False MinimizeBox: False ShowInTaskbar: False

To add a new form to the application, in the Solution Explorer, right- click SolasPropertyRental1 -> Add -> Windows Form...
Set the Name to RentalProperties and press Enter
From the Toolbox, add a ListView to the form

While the new list view is still selected, in the Properties window, click the ellipsis button of the Columns field and create the columns as follows:

(Name)	Text	TextAlign	Width
colPropertyCode	Prop Code		65
colPropertyType	Property Type		85
colBedrooms	Bedrooms	Right	65
colBathrooms	Bathrooms	Right	65
colMonthlyRent	Monthly Rent	Right	75
colStatus	Status		65

Design the form as follows:

Control	Text	Name	Other Properties
ListView		lvwProperties	View: Details GridLines: True FullRowSelect: True Anchor: Top, Bottom, Left, Right
Button	New Property...	btnNewProperty	Anchor: Bottom, Right
Button	Close	btnClose	Anchor: Bottom, Right

Double-click an unoccupied area of the Rental Properties form and implement the Load event as follows:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO;
using System.Xml;

namespace SolasPropertyRental1
{
    public partial class RentalProperties : Form
    {
        public RentalProperties()
        {
            InitializeComponent();
        }

        void ShowProperties()
        {
            XmlDocument docProperties = new XmlDocument();
            string Filename = @"C:\Solas Property Rental\properties.xml";

            if (File.Exists(Filename))
            {
                lvwProperties.Items.Clear();

                docProperties.Load(Filename);
                XmlElement elmProperty = docProperties.DocumentElement;
                XmlNodeList lstProperties = elmProperty.ChildNodes;

                foreach (XmlNode node in lstProperties)
                {
                    ListViewItem lviProperty = new ListViewItem(node.FirstChild.InnerText); // Property Code

                    lviProperty.SubItems.Add(node.FirstChild.NextSibling.InnerText); // Property Type
                    lviProperty.SubItems.Add(node.FirstChild.NextSibling.NextSibling.InnerText); // Bedrooms
                    lviProperty.SubItems.Add(node.FirstChild.NextSibling.NextSibling.NextSibling.InnerText); // Bathrooms
                    lviProperty.SubItems.Add(node.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling.InnerText); // Monthly Rent
                    lviProperty.SubItems.Add(node.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.InnerText); // Status
                    lvwProperties.Items.Add(lviProperty);
                }
            }
        }

        private void RentalProperties_Load(object sender, EventArgs e)
        {
            ShowProperties();
        }
    }
}

To add another form to the application, in the Solution Explorer, right- click SolasPropertyRental1 -> Add -> Windows Form...
Set the Name to PropertyEditor and click Add

Design the form as follows:

Control	Text	Name	Properties
Label	Property Code:
MaskedTextBox		txtPropertyCode	Mask: 000-000 Modifiers: Public
Button	OK	btnOK	DialogResult: OK
Label	Property Type:
ComboBox		cbxPropertyTypes	Modifiers: Public Items: Unknown Apartment Townhouse Single Family
Button	Cancel	btnCancel	DialogResult: Cancel
Label	Bedrooms:
TextBox	0	txtBedrooms	TextAlign: Right Modifiers: Public
Label	Bathrooms:
TextBox	0.00	txtBathrooms	TextAlign: Right Modifiers: Public
Label	Monthly Rent:
TextBox	0.00	txtMonthlyRent	TextAlign: Right Modifiers: Public
Label	Occupancy Status:
ComboBox	Unknown	cbxStatus	Modifiers: Public Items: Unknown Available Occupied Needs Repair
Form			AcceptButton: btnOK CancelButton: btnCancel FormBorderStyle: FixedDialog MaximizeBox: False MinimizeBox: False ShowInTaskbar: False

To add a new form to the application, in the Solution Explorer, right-click SolasPropertyRental1 -> Add -> Windows Form...
Set the Name to RentalAllocation and click Add
From the Toolbox, add a ListView to the form

Design the form as follows:

Solas Property Rental: Rental Allocation

Control	Text	Name	Other Properties
Label	Rent Allocation		AutoSize: False BackColor: Gray BorderStyle: FixedSingle ForeColor: White TextAlign: MiddleLeft
Label	Allocation Code:
MaskedTextBox		txtAllocationCode	Mask: 0000-9999 Modifiers: Public
Label	Date Allocated:
DateTimePicker		dtpDateAllocated	Format: Short Modifiers: Public
Label	Tenant		AutoSize: False BackColor: Gray BorderStyle: FixedSingle ForeColor: White TextAlign: MiddleLeft
Label	Property		AutoSize: False BackColor: Gray BorderStyle: FixedSingle ForeColor: White TextAlign: MiddleLeft

Label	Account #:
MaskedTextBox		txtTenantAcntNbr	Mask: 00-00-00 Modifiers: Public
Label	Property #:
MaskedTextBox		txtPropertyCode	Mask: 000-000 Modifiers: Public
Label	Tenant Name
TextBox		txtTenantName	Modifiers: Public
Label	Property Type:
TextBox		txtPropertyType	Modifiers: Public
Label	Marital Status:
TextBox		txtMaritalStatus	Modifiers: Public
Label	Monthly Rent:
TextBox		txtMonthlyRent
Label	Allocation Evaluation		AutoSize: False BackColor: Gray BorderStyle: FixedSingle ForeColor: White TextAlign: MiddleLeft
Label	Contract Length:
ComboBox		cbxContractLength	Items: Monthly 3 Months 6 Months 12 Months Modifiers: Public
Label	Rent Start Date:
DateTimePicker		dtpRentStartDate	Modifiers: Public
Button	OK	btnOK	DialogResult: OK
Button	Close	btnClose	DialogResult: Cancel
Form			AcceptButton: btnOK CancelButton: btnClose FormBorderStyle: FixedDialog MaximizeBox: False MinimizeBox: False ShowInTaskbar: False

On the form, click the Account # text box and, in the Properties window, double-click Leave

Implement the event as follows:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO;
using System.Xml;

namespace SolasPropertyRental1
{
    public partial class RentalAllocation : Form
    {
        public RentalAllocation()
        {
            InitializeComponent();
        }

        private void txtTenantAcntNbr_Leave(object sender, EventArgs e)
        {
            string Filename = @"C:\Solas Property Rental\tenants.xml";
            XmlDocument docTenants = new XmlDocument();

            if (File.Exists(Filename))
            {
                docTenants.Load(Filename);
                XmlElement elmTenant = docTenants.DocumentElement;
                XmlNodeList lstTenants = elmTenant.ChildNodes;
                bool TenantFound = false;

                for (int i = 0; i < lstTenants.Count; i++)
                {
                    XmlNode node = lstTenants[i];

                    if (node.FirstChild.InnerText == txtTenantAcntNber.Text)
                    {
                        TenantFound = true;
                        txtTenantName.Text = node.FirstChild.NextSibling.InnerText;
                        txtMaritalStatus.Text = node.FirstChild.NextSibling.NextSibling.InnerText;
                    }
                }

                if (TenantFound == false)
                {
                    MessageBox.Show("There is no tenant with that account number");
                    txtTenantAcntNber.Text = "";
                }
            }
            else
                MessageBox.Show("There is no list of tenants to check.");
        }
    }
}

Return to the Rent Allocation form and click the Property Code text box
In the Events section of the Properties window, double-click Leave

Implement the event as follows:

private void txtPropertyCode_Leave(object sender, EventArgs e)
{
    string Filename = @"C:\Solas Property Rental\properties.xml";
    XmlDocument docProperties = new XmlDocument();

    if (File.Exists(Filename))
    {
        docProperties.Load(Filename);
        XmlElement elmProperty = docProperties.DocumentElement;
        XmlNodeList lstProperties = elmProperty.ChildNodes;
        bool PropertyFound = false;

        for (int i = 0; i < lstProperties.Count; i++)
        {
            XmlNode node = lstProperties[i];

            if (node.FirstChild.InnerText == txtPropertyCode.Text)
            {
                PropertyFound = true;
                txtPropertyType.Text = node.FirstChild.NextSibling.InnerText;
                txtMonthlyRent.Text = node.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling.InnerText;
            }
        }

        if (PropertyFound == false)
        {
            MessageBox.Show("There is no Property with that code");
            txtPropertyType.Text = "";
        }
    }
    else
        MessageBox.Show("There is no list of properties to check.");
}

To add a new form to the application, in the Solution Explorer, right- click SolasPropertyRental1 -> Add -> Windows Form...
Set the Name to RentalAllocations and press Enter
From the Toolbox, add a ListView to the form

While the new list view is still selected, in the Properties window, click the ellipsis button of the Columns field and create the columns as follows:

(Name)	Text	TextAlign	Width
colAllocationCode	Alloc Code		65
colDateAllocated	Date Allocated	Center	85
colTenantAccount	Tenant #	Center	65
colTenantName	Tenant Name		100
colPropertyCode	Prop Code	Center	65
colPropertyType	Prop Type		75
colContractLength	Contract Length		88
colRentStartDate	Rent Start Date	Center	88
colMonthlyRent	Monthly Rent	Right	76

Design the form as follows:

Solas Property Rental: Rental Allocations

Control	Text	Name	Other Properties
ListView		lvwAllocations	View: Details GridLines: True FullRowSelect: True Anchor: Top, Bottom, Left, Right
Button	New Rental Allocation...	btnNewAllocation	Anchor: Bottom, Right
Button	Close	btnClose

Double-click an unoccupied area of the RentalAllocations form and implement the Load event as follows:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO;
using System.Xml;

namespace SolasPropertyRental1
{
    public partial class RentalAllocations : Form
    {
        public RentalAllocations()
        {
            InitializeComponent();
        }

        void ShowRentalAllocations()
        {
            string Filename = @"C:\Solas Property Rental\contracts.xml";
            XmlDocument docAllocations = new XmlDocument();

            if (File.Exists(Filename))
            {
                lvwAllocations.Items.Clear();

                docAllocations.Load(Filename);
                XmlElement elmAllocation = docAllocations.DocumentElement;
                XmlNodeList lstAllocations = elmAllocation.ChildNodes;

                foreach (XmlNode node in lstAllocations)
                {
                    ListViewItem lviAllocation = new ListViewItem(node.FirstChild.InnerText); // Allocation Code

                    lviAllocation.SubItems.Add(node.FirstChild.NextSibling.InnerText); // Date Allocated
                    lviAllocation.SubItems.Add(node.FirstChild.NextSibling.NextSibling.InnerText); // Tenant Account Number
                    lviAllocation.SubItems.Add(node.FirstChild.NextSibling.NextSibling.NextSibling.InnerText); // Tenant Name
                    lviAllocation.SubItems.Add(node.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.InnerText); // Property Code
                    lviAllocation.SubItems.Add(node.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.InnerText); // Property Type
                    lviAllocation.SubItems.Add(node.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.InnerText); // Contract Length
                    lviAllocation.SubItems.Add(node.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.InnerText); // Rent Start Date
                    lviAllocation.SubItems.Add(node.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.InnerText); // Monthly Rent
                    lvwAllocations.Items.Add(lviAllocation);
                }
            }
        }

        private void RentalAllocations_Load(object sender, EventArgs e)
        {
            ShowRentalAllocations();
        }
    }
}

To add a new form to the application, in the Solution Explorer, right-click SolasPropertyRental1 -> Add -> Windows Form...
Set the Name to RentPayment and click Add

Design the form as follows:

Control	Text	Name	Other Properties
Label	Rent Allocation		AutoSize: False BackColor: Gray BorderStyle: FixedSingle ForeColor: White TextAlign: MiddleLeft
Label	Date Received:
DateTimePicker		dtpDateReceived	Format: Short Modifiers: Public
Label	Allocation Code:
MaskedTextBox		txtAllocationCode	Mask: 0000-9999 Modifiers: Public
Label	Receipt #:
TextBox		txtReceiptNumber	Modifiers: Public
Label	Tenant Account #:
TextBox		txtTenantAcntNber	Modifiers: Public
Label	Property Code:
TextBox		txtPropertyCode	Modifiers: Public
Label	Tenant Name:
TextBox		txtTenantName	Modifiers: Public
Label	Property Type:
TextBox		txtPropertyType	Modifiers: Public
Label	Payment Summary		AutoSize: False BackColor: Gray BorderStyle: FixedSingle ForeColor: White TextAlign: MiddleLeft
Label	Month:
Label	Year:
Label	Payment For:
ComboBox		cbxMonths	Modifiers: Public Items: January February March April May June July August September October November December
TextBox		txtYear	Modifiers: Public
Label	Amount Received:
TextBox	0.00	txtAmountReceived	TextAlign: Right Modifiers: Public
Button	OK	btnOK	DialogResult: OK
Button	Close	btnClose	DialogResult: Cancel
Form			AcceptButton: btnOK CancelButton: btnClose FormBorderStyle: FixedDialog MaximizeBox: False MinimizeBox: False ShowInTaskbar: False

On the form, click the Allocation Code text box and, in the Events section of the Properties window, double-click Leave

Implement the event as follows:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO;
using System.Xml;

namespace SolasPropertyRental1
{
    public partial class RentPayment : Form
    {
        public RentPayment()
        {
            InitializeComponent();
        }

        private void txtAllocationCode_Leave(object sender, EventArgs e)
        {
            string Filename = @"C:\Solas Property Rental\contracts.xml";
            XmlDocument docAllocations = new XmlDocument();

            if (File.Exists(Filename))
            {
                docAllocations.Load(Filename);
                XmlElement elmAllocation = docAllocations.DocumentElement;
                XmlNodeList lstAllocations = elmAllocation.ChildNodes;
                bool ContractFound = false;

                for (int i = 0; i < lstAllocations.Count; i++)
                {
                    XmlNode node = lstAllocations[i];

                    if (node.FirstChild.InnerText == txtAllocationCode.Text)
                    {
                        ContractFound = true;
                        txtTenantAcntNber.Text = node.FirstChild.NextSibling.NextSibling.InnerText;
                        txtTenantName.Text = node.FirstChild.NextSibling.NextSibling.NextSibling.InnerText;
                        txtPropertyCode.Text = node.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.InnerText;
                        txtPropertyType.Text = node.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.InnerText;
                        txtAmountReceived.Text = node.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.InnerText;
                    }
                }

                if (ContractFound == false)
                {
                    MessageBox.Show("There is no rental contral with that number");
                    txtTenantAcntNber.Text = "";
                }
            }
            else
                MessageBox.Show("There is no list of rental contracts to check.");
        }
    }
}

To add a new form to the application, in the Solution Explorer, right- click SolasPropertyRental1 -> Add -> Windows Form...
Set the Name to RentPayments and press Enter
From the Toolbox, add a ListView to the form

While the new list view is still selected, in the Properties window, click the ellipsis button of the Columns field and create the columns as follows:

(Name)	Text	TextAlign	Width
colReceiptNumber	Receipt #	Right
colDateReceived	Date Received	Center	85
colAllocationCode	Alloc Code	Center	65
colTenantAccount	Tenant #	Center	65
colTenantName	Tenant Name		100
colPropertyCode	Prop Code	Center	65
colPropertyType	Prop Type		75
colPaymentFor	Payment For		88
colAmountReceived	Amount	Right	50

Design the form as follows:

Control	Text	Name	Other Properties
ListView		lvwRentPayments	View: Details GridLines: True FullRowSelect: True Anchor: Top, Bottom, Left, Right
Button	New Rent Payment...	btnNewPayment	Anchor: Bottom, Right
Button	Close	btnClose	Anchor: Bottom, Right

Double-click an unoccupied area of the RentPayments form and implement the Load event as follows:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO;
using System.Xml;

namespace SolasPropertyRental1
{
    public partial class RentPayments : Form
    {
        public RentPayments()
        {
            InitializeComponent();
        }

        void ShowRentPayments()
        {
            string Filename = @"C:\Solas Property Rental\payments.xml";
            XmlDocument docPayments = new XmlDocument();

            if (File.Exists(Filename))
            {
                lvwRentPayments.Items.Clear();

                docPayments.Load(Filename);
                XmlElement elmAllocation = docPayments.DocumentElement;
                XmlNodeList lstAllocations = elmAllocation.ChildNodes;

                foreach (XmlNode node in lstAllocations)
                {
                    ListViewItem lviPayment = new ListViewItem(node.FirstChild.InnerText); // Receipt Number

                    lviPayment.SubItems.Add(node.FirstChild.NextSibling.InnerText); // Date Received
                    lviPayment.SubItems.Add(node.FirstChild.NextSibling.NextSibling.InnerText); // Allocation Code
                    lviPayment.SubItems.Add(node.FirstChild.NextSibling.NextSibling.NextSibling.InnerText); // Tenant Account Number
                    lviPayment.SubItems.Add(node.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling.InnerText);  // Tenant Name
                    lviPayment.SubItems.Add(node.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.InnerText); // Property Code
                    lviPayment.SubItems.Add(node.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.InnerText); // Property Type
                    lviPayment.SubItems.Add(node.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.InnerText); // Payment For
                    lviPayment.SubItems.Add(node.FirstChild.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.NextSibling.InnerText); // Amount
                    lvwRentPayments.Items.Add(lviPayment);
                }
            }
        }

        private void RentPayments_Load(object sender, EventArgs e)
        {
            ShowRentPayments();
        }
    }
}

In the Solution Explorer, right-click Form1.cs and click Rename
Set the name to Central.cs and press Enter twice to display the form

Design the form as follows:

Control	Text	Name
Button	Tenants	btnTenants
Button	Rental Properties	btnRentalProperties
Button	Rental Allocations	btnRentalAllocations
Button	C&lose	btnClose

Double-click the Rent Payment button and implement its event as follows:

private void btnRentPayment_Click(object sender, EventArgs e)
{
    RentPayments frmPayment = new RentPayments();
    frmPayment.Show();
}

Return to the Central form

Double-click the Rental Allocations button and implement its event as follows:

private void btnRentalAllocations_Click(object sender, EventArgs e)
{
    RentalAllocations frmAllocations = new RentalAllocations();
    frmAllocations.ShowDialog();
}

Return to the Central form

Double-click the Tenants button and implement its event as follows:

private void btnTenants_Click(object sender, EventArgs e)
{
    Tenants frmTenants = new Tenants();
    frmTenants.ShowDialog();
}

Return to the Central form

Double-click the Rental Properties button and implement its event as follows:

private void btnRentalProperties_Click(object sender, EventArgs e)
{
    RentalProperties frmProperties = new RentalProperties();
    frmProperties.ShowDialog();
}

Return to the Central form

Double-click the Close button and implement its event as follows:

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

Save all

Appending an Element

To assist with programmatically creating a new element, the XmlDocument class provides the CreateElement() method that is overloaded with three versions. One of the versions uses the following syntax:

public XmlElement CreateElement(string name);

Using this method, to create a new element, call it and pass it the name of the element. For example, imagine you want to add a new Title element to the above file. You would start with code as follows:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO;
using System.Xml;

namespace videoCollection1
{
    public partial class Exercise : Form
    {
        public Exercise()
        {
            InitializeComponent();
        }

        private void btnDocument_Click(object sender, EventArgs e)
        {
            string Filename = "videos.xml";
            XmlDocument DOMVideos = new XmlDocument();

            if (File.Exists(Filename))
            {
                DOMVideos.Load(Filename);

                XmlElement elmNew = DOMVideos.CreateElement("Title");
            }
        }
    }
}

In order to add the new element to the file, you must specify its position in the tree: whether it would be the first or the last node, whether you want to position it before or after a node of your choice. For example, if you want to add a new Title element to the above file, it would be considered a child of the root, that is, a child of the XmlDocument.DocumentElement property. In the previous lesson, we learned how to get a reference to the root node.

To support the positions of existing nodes, the XmlNode class, which is the ancestor of all XML nodes of the .NET Framework, provides various appropriate methods. One of these methods is AppendChild(), which is used to add an element as the last child of its parent. The syntax of the XmlNode.AppendChild() method is:

public virtual XmlNode AppendChild(XmlNode newChild);

When calling this method, pass the XmlNode object you had previous created. After adding the node, if you want the file to keep it, you should save it. Here is an example:

private void btnDocument_Click(object sender, EventArgs e)
{
    string Filename = "videos.xml";
    XmlDocument DOMVideos = new XmlDocument();

    if (File.Exists(Filename))
    {
        DOMVideos.Load(Filename);

        XmlElement elmRoot = DOMVideos.DocumentElement;
        XmlElement elmNew = DOMVideos.CreateElement("title");
        elmRoot.AppendChild(elmNew);
    }
    else // if (!File.Exists(Filename))
    {
        // Create the default XML structure
        DOMVideos.LoadXml("<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
                          "<videos></videos>");
    }
            
    DOMVideos.Save(Filename);
}

This would produce:

<?xml version="1.0" encoding="utf-8"?>
<videos />

or:

<?xml version="1.0" encoding="utf-8"?>
<videos>
  <title />
</videos>

Notice that the newly added element is empty.

Adding the Inner Text of an Element

Suppose you have the following videos.xml file:

<?xml version="1.0" encoding="utf-8"?>
<videos>
  <video>
    <title>The Distinguished Gentleman</title>
    <director>Jonathan Lynn</director>
    <length>112 Minutes</length>
    <format>DVD</format>
    <rating>R</rating>
  </video>
  <video>
    <title>Her Alibi</title>
    <director>Bruce Beresford</director>
    <length>94 Minutes</length>
    <format>DVD</format>
    <rating>PG-13</rating>
  </video>
</videos>

Imagine that you want to add a video element. You have a choice of adding one, more than one, or all child elements of the video node. To perform this operation, one solution you can use is to "build" all child elements of the video element, then add the node as a whole.

In the previous lesson, we saw that the XmlNode.InnerXml property comprises a node, its markup, its children and their markup. This means that you can create the child node(s) with its (their) markup(s) as a string and assign that string to an XmlNode.InnerXml string. To do this, you would need the set version of the InnerXml property. It is declared as follows:

public virtual string InnerXml{get; set;}

Here is an example that adds a complete new video node to the above XML file:

private void btnDocument_Click(object sender, EventArgs e)
{
    string Filename = "videos.xml";
    XmlDocument DOMVideos = new XmlDocument();

    if (File.Exists(Filename))
    {
        DOMVideos.Load(Filename);

        XmlElement elmXML = DOMVideos.CreateElement("video");
        string strNewvideo = "<title>Other People's Money</title>" +
                             "<director>Alan Brunstein</director>" +
                             "<length>114 Minutes</length>" +
                             "<format>VHS</format>" +
                             "<rating>PG-13</rating>";

        elmXML.InnerXml = strNewvideo;
        DOMVideos.DocumentElement.AppendChild(elmXML);
    }
    else // if (!File.Exists(Filename))
    {
        // Create the default XML structure
        DOMVideos.LoadXml("<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
                          "<videos></videos>");
    }
            
    DOMVideos.Save(Filename);
}

This would produce:

<?xml version="1.0" encoding="utf-8"?>
<videos>
  <video>
    <title>Other People's Money</title>
    <director>Alan Brunstein</director>
    <length>114 Minutes</length>
    <format>VHS</format>
    <rating>PG-13</rating>
  </video>
</videos>

Practical Learning: Introducing operations on XML Elements

Access the Tenants.cs [Design] tab and double-click the New Tenant button

Implement the Click event as follows:

private void btnNewTenant_Click(object sender, EventArgs e)
{
    string AccountNumber;
    string FullName, MaritalStatus, PhoneNumber;

    // If this directory doesn't exist, create it
    Directory.CreateDirectory(@"C:\Solas Property Rental\");
    // This is the XML file that holds the list of tenants
    string Filename = @"C:\Solas Property Rental\tenants.xml";
    // This is the dialog box from where a tenant is created
    TenantEditor editor = new TenantEditor();

    // Display the Tenant Editor Dialog and find out if the 
    // user clicked OK after filling its controls
    if (editor.ShowDialog() == DialogResult.OK)
    {
        // We will need a reference to the XML document
        XmlDocument docTenant = new XmlDocument();

        // Find out if the file exists already
        // If it doesn't, then create it
        if (!File.Exists(Filename))
        {
            docTenant.LoadXml("<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
                              "<Tenants></Tenants>");
            docTenant.Save(Filename);
        }

        // At this time, we have a Tenants.xml file. Open it
        docTenant.Load(Filename);

        // Get a reference to the root node
        XmlElement nodRoot = docTenant.DocumentElement;

        // Prepare the values of the XML element
        AccountNumber = editor.txtAccountNumber.Text;
        FullName = editor.txtFullName.Text;
        MaritalStatus = editor.cbxMaritalStatus.Text;
        PhoneNumber = editor.txtPhoneNumber.Text;

        // Create an element named Tenant
        XmlElement elmXML = docTenant.CreateElement("Tenant");
        // Create the XML code of the child element of Tenant
        string strNewCustomer = "<AccountNumber>" + AccountNumber +
                                "</AccountNumber>" +
                                "<FullName>" + FullName +
                                "</FullName>" +
                                "<MaritalStatus>" + MaritalStatus
                                + "</MaritalStatus>" +
                                "<PhoneNumber>" + PhoneNumber +
				"</PhoneNumber>";
        elmXML.InnerXml = strNewCustomer;
        // Append the new element as a child of Tenant
        docTenant.DocumentElement.AppendChild(elmXML);

        // Save the XML file
        docTenant.Save(@"C:\Solas Property Rental\tenants.xml");
        // Since the content of the XML file has just been changed,
        // re-display the list of tenants
        ShowTenants();
    }
}

Return to the Tenants form and double-click the Close button

Implement its Click event as follows:

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

Access the RentalProperties.cs [Design] tab and double-click the New Property button

Implement the Click event as follows:

private void btnNewProperty_Click(object sender, EventArgs e)
{
    // If this directory doesn't exist, create it
    Directory.CreateDirectory(@"C:\Solas Property Rental\");
    // This is the XML file that holds the list of proeprties
    string Filename = @"C:\Solas Property Rental\properties.xml";
    PropertyEditor editor = new PropertyEditor();

    Random rnd = new Random();
    editor.txtPropertyCode.Text = rnd.Next(100000, 999999).ToString();

    if (editor.ShowDialog() == DialogResult.OK)
    {
        string PropertyCode, PropertyType, Status;
        int Bedrooms;
        float Bathrooms;
        double MonthlyRent;

        // We will need a reference to the XML document
        XmlDocument docProperty = new XmlDocument();

        // Find out if the file exists already
        // If it doesn't, then create it
        if (!File.Exists(Filename))
        {
            docProperty.LoadXml("<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
                                "<Properties></Properties>");
            docProperty.Save(Filename);
        }

        // Open the XML file
        docProperty.Load(Filename);

        // Get a reference to the root node
        XmlElement nodRoot = docProperty.DocumentElement;

        PropertyCode = editor.txtPropertyCode.Text;
        PropertyType = editor.cbxPropertyTypes.Text;
        Bedrooms = int.Parse(editor.txtBedrooms.Text);
        Bathrooms = float.Parse(editor.txtBathrooms.Text);
        MonthlyRent = double.Parse(editor.txtMonthlyRent.Text);
        Status = editor.cbxStatus.Text;

        XmlElement elmXML = docProperty.CreateElement("Property");
        string strNewCustomer = "<PropertyCode>" + PropertyCode +
                                "</PropertyCode>" + "<PropertyType>" +
                                PropertyType + "</PropertyType>" +
                                "<Bedrooms>" + Bedrooms + "</Bedrooms>" +
                                "<Bathrooms>" + Bathrooms.ToString("F") +
				"</Bathrooms>" + "<MonthlyRent>" +
				MonthlyRent.ToString("F") + 
				"</MonthlyRent>" +
                                "<Status>" + Status + "</Status>";

        elmXML.InnerXml = strNewCustomer;
        docProperty.DocumentElement.AppendChild(elmXML);

        docProperty.Save(@"C:\Solas Property Rental\properties.xml");
        ShowProperties();
    }
}

Return to the Rental Properties form and double-click the Close button

Implement its Click event as follows:

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

Execute the application

Use the Tenants button and its New Tenant button to create the following Tenants:

Account #	Full Name	Marital Status	Phone #
20-48-46	Lenny Crandon	Single	(240) 975-9093
57-97-15	Joan Ramey	Married	(301) 304-5845
19-38-84	Peter Sellars	Married	(240) 801-7974
24-68-84	Alberta Sanson	Separated	(202) 917-0095
47-80-95	Urlus Flack	Single	(703) 203-7947

Use the Rental Properties button and its New Property button to create the following properties:

Prop Code	Property Types	Bedrooms	Bathrooms	Monthly Rent	Status
527-992	Apartment	1	1	925	Available
726-454	Apartment	2	1	1150.5	Available
476-473	Single Family	5	3.5	2250.85	Occupied
625-936	Townhouse	3	2.5	1750	Available
179-738	Townhouse	4	2.5	1920.5	Available
727-768	Single Family	4	2.5	2140.5	Needs Repair
371-801	Apartment	3	2	1250.25	Available
241-536	Townhouse	3	1.5	1650.5	Occupied

Close the forms and return to your programming environment

Adding an Element With Value

Consider the following XML file named videos.xml:

<?xml version="1.0" encoding="utf-8" ?>
<videos>
  <title>The Distinguished Gentleman</title>
</videos>

If you want the element to have a value, the XmlDocument class provides the CreateTextNode() method. This method returns an XmlText value. The syntax of this method is:

public virtual XmlText CreateTextNode(string text);

This method takes as argument the string that would constitute the value of the element. Before calling it, you should have used the XmlNode.AppendChild() method to create a node. Calling this method on the LastChild node of the one that called the AppendChild() would specify the value of the new node. Here is an example:

private void btnDocument_Click(object sender, EventArgs e)
{
    string Filename = "videos.xml";
    XmlDocument DOMVideos = new XmlDocument();

    if (File.Exists(Filename))
    {
        DOMVideos.Load(Filename);

        XmlElement elmRoot = DOMVideos.DocumentElement;

        XmlElement elmNew = DOMVideos.CreateElement("title");
        XmlText txtvideo = DOMVideos.CreateTextNode("Basic Instinct");
        elmRoot.AppendChild(elmNew);
        elmRoot.LastChild.AppendChild(txtvideo);
    }
    else // if (!File.Exists(Filename))
    {
        // Create the default XML structure
        DOMVideos.LoadXml("<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
                          "<videos></videos>");
    }
            
    DOMVideos.Save(Filename);
}

This would produce:

<?xml version="1.0" encoding="utf-8"?>
<videos>
  <title>The Distinguished Gentleman</title>
  <title>Basic Instinct</title>
</videos>

The combination of calls to XmlDocument.CreateElement() and XmlDocument.CreateTextNode() allow you to create a new element that has a value.

Consider the following XML file named "videos.xml":

<?xml version="1.0" encoding="utf-8"?>
<videos>
  <video>
    <title>The Distinguished Gentleman</title>
  </video>
  <video>
    <title>Basic Instinct</title>
  </video>
</videos>

Notice that the root, videos, has a repetitive child named video. This video child has its own child named Title. Imagine that you want to add a new video node that has a child. To do this, first create an empty video node as a child of the root. We learned earlier how to do that:

private void btnDocument_Click(object sender, EventArgs e)
{
    string Filename = "videos.xml";
    XmlDocument DOMVideos = new XmlDocument();

    if (File.Exists(Filename))
    {
        DOMVideos.Load(Filename);

        XmlElement elmRoot = DOMVideos.DocumentElement;
        XmlElement elmNew = DOMVideos.CreateElement("video");
        elmRoot.AppendChild(elmNew);
    }
    else // if (!File.Exists(Filename))
    {
        // Create the default XML structure
        DOMVideos.LoadXml("<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
                          "<videos></videos>");
    }
            
    DOMVideos.Save(Filename);
}

After creating the new child of the root, initialize the grand child with the desired name (the name doesn't have to be one of the existing names) and a value (which is optional if you don't want the new node to have a value). Once the new node is ready, append it as the last child of the root. If this new node has a value, append its XmlText object as the LastChild of the LastChild of the root. Here is an example of how you would do this:

private void btnDocument_Click(object sender, EventArgs e)
{
    string Filename = "videos.xml";
    XmlDocument DOMVideos = new XmlDocument();

    if (File.Exists(Filename))
    {
        DOMVideos.Load(Filename);

        XmlElement elmRoot = DOMVideos.DocumentElement;
        XmlElement elmNew = DOMVideos.CreateElement("video");
        elmRoot.AppendChild(elmNew);

        elmRoot = DOMVideos.DocumentElement;

        elmNew = DOMVideos.CreateElement("title");
        XmlText txtvideo = DOMVideos.CreateTextNode("Her Alibi");

        elmRoot.LastChild.AppendChild(elmNew);
        elmRoot.LastChild.LastChild.AppendChild(txtvideo);
    }
    else // if (!File.Exists(Filename))
    {
        // Create the default XML structure
        DOMVideos.LoadXml("<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
                          "<videos></videos>");
    }
            
    DOMVideos.Save(Filename);
}

This would produce:

<?xml version="1.0" encoding="utf-8"?>
<videos>
  <video>
    <title>The Distinguished Gentleman</title>
  </video>
  <video>
    <title>Basic Instinct</title>
  </video>
  <video>
    <title>Her Alibi</title>
  </video>
</videos>

Now consider the following file:

<?xml version="1.0" encoding="utf-8"?>
<videos>
  <video>
    <title>The Distinguished Gentleman</title>
    <director>Jonathan Lynn</director>
    <length>112 Minutes</length>
    <format>DVD</format>
    <rating>R</rating>
  </video>
  <video>
    <title>Her Alibi</title>
    <director>Bruce Beresford</director>
    <length>94 Minutes</length>
    <format>DVD</format>
    <rating>PG-13</rating>
  </video>
</videos>

The root, videos, has a child named video. The video node has many child nodes. By now, we know how to add a child to the root. We also saw how to add a grand child with value to the root. To had many (grand) children to a node, first build the node, add it to the root, then continuously add the necessary nodes, one at a time, including its name and its optional value. This would be done as follows:

private void btnDocument_Click(object sender, EventArgs e)
{
    string Filename = "videos.xml";
    XmlDocument DOMVideos = new XmlDocument();

    if (File.Exists(Filename))
    {
        DOMVideos.Load(Filename);

        XmlElement elmRoot = DOMVideos.DocumentElement;
        XmlElement elmNew = DOMVideos.CreateElement("video");
        elmRoot.AppendChild(elmNew);

        elmRoot = DOMVideos.DocumentElement;

        elmNew = DOMVideos.CreateElement("title");
        XmlText txtvideo = DOMVideos.CreateTextNode("The Day After Tomorrow");
        elmRoot.LastChild.AppendChild(elmNew);
        elmRoot.LastChild.LastChild.AppendChild(txtvideo);

        elmNew = DOMVideos.CreateElement("director");
        txtvideo = DOMVideos.CreateTextNode("Roland Emmerich");
        elmRoot.LastChild.AppendChild(elmNew);
        elmRoot.LastChild.LastChild.AppendChild(txtvideo);

        elmNew = DOMVideos.CreateElement("length");
        txtvideo = DOMVideos.CreateTextNode("124 Minutes");
        elmRoot.LastChild.AppendChild(elmNew);
        elmRoot.LastChild.LastChild.AppendChild(txtvideo);

        elmNew = DOMVideos.CreateElement("format");
        txtvideo = DOMVideos.CreateTextNode("DVD");
        elmRoot.LastChild.AppendChild(elmNew);
        elmRoot.LastChild.LastChild.AppendChild(txtvideo);

        elmNew = DOMVideos.CreateElement("rating");
        txtvideo = DOMVideos.CreateTextNode("PG-13");
        elmRoot.LastChild.AppendChild(elmNew);
        elmRoot.LastChild.LastChild.AppendChild(txtvideo);
    }
    else // if (!File.Exists(Filename))
    {
        // Create the default XML structure
        DOMVideos.LoadXml("<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
                          "<videos></videos>");
    }
            
    DOMVideos.Save(Filename);
}

This would produce:

<?xml version="1.0" encoding="utf-8"?>
<videos>
  <video>
    <title>The Distinguished Gentleman</title>
    <director>Jonathan Lynn</director>
    <length>112 Minutes</length>
    <format>DVD</format>
    <rating>R</rating>
  </video>
  <video>
    <title>Her Alibi</title>
    <director>Bruce Beresford</director>
    <length>94 Minutes</length>
    <format>DVD</format>
    <rating>PG-13</rating>
  </video>
  <video>
    <title>The Day After Tomorrow</title>
    <director>Roland Emmerich</director>
    <length>124 Minutes</length>
    <format>DVD</format>
    <rating>PG-13</rating>
  </video>
</videos>

Using the same approach, you can add children to children of children, and so on.

Practical Learning: Programmatically Adding an Element

Access the Rental Allocations form and double-click the New Allocation button

Implement the event as follows:

private void btnNewAllocation_Click(object sender, EventArgs e)
{
    string AllocationCode, TenantAccountNumber,
           TenantName, MaritalStatus,
           PropertyCode, PropertyType, ContractLength;
    DateTime DateAllocated, RentStartDate;
    double MonthlyRent;

    RentalAllocation editor = new RentalAllocation();
    Directory.CreateDirectory(@"C:\Solas Property Rental");
    string Filename = @"C:\Solas Property Rental\contracts.xml";

    if (editor.ShowDialog() == DialogResult.OK)
    {
        XmlDocument docAllocation = new XmlDocument();

        if (!File.Exists(Filename))
        {
    docAllocation.LoadXml("<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
                                  "<Allocations></Allocations>");
            docAllocation.Save(Filename);
        }

        docAllocation.Load(Filename);

        XmlElement nodRoot = docAllocation.DocumentElement;

        AllocationCode = editor.txtAllocationCode.Text;
        DateAllocated = editor.dtpDateAllocated.Value;
        TenantAccountNumber = editor.txtTenantAcntNber.Text;
        TenantName = editor.txtTenantName.Text;
        MaritalStatus = editor.txtMaritalStatus.Text;
        PropertyCode = editor.txtPropertyCode.Text;
        PropertyType = editor.txtPropertyType.Text;
        MonthlyRent = double.Parse(editor.txtMonthlyRent.Text);
        ContractLength = editor.cbxContractLengths.Text;
        RentStartDate = editor.dtpRentStartDate.Value;

        XmlElement elmRoot = docAllocation.DocumentElement;
        XmlElement elmAllocation =
		docAllocation.CreateElement("RentalAllocation");
        elmRoot.AppendChild(elmAllocation);

        elmRoot = docAllocation.DocumentElement;

        elmAllocation = docAllocation.CreateElement("AllocationCode");
        XmlText txtAllocation =
		docAllocation.CreateTextNode(AllocationCode);
        elmRoot.LastChild.AppendChild(elmAllocation);
        elmRoot.LastChild.LastChild.AppendChild(txtAllocation);

        elmAllocation = docAllocation.CreateElement("DateAllocated");
        txtAllocation =
		docAllocation.CreateTextNode(DateAllocated.ToString("d"));
        elmRoot.LastChild.AppendChild(elmAllocation);
        elmRoot.LastChild.LastChild.AppendChild(txtAllocation);

        elmAllocation = docAllocation.CreateElement("TenantAccountNumber");
        txtAllocation = docAllocation.CreateTextNode(TenantAccountNumber);
        elmRoot.LastChild.AppendChild(elmAllocation);
        elmRoot.LastChild.LastChild.AppendChild(txtAllocation);

        elmAllocation = docAllocation.CreateElement("TenantName");
        txtAllocation = docAllocation.CreateTextNode(TenantName);
        elmRoot.LastChild.AppendChild(elmAllocation);
        elmRoot.LastChild.LastChild.AppendChild(txtAllocation);

        elmAllocation = docAllocation.CreateElement("MaritalStatus");
        txtAllocation = docAllocation.CreateTextNode(MaritalStatus);
        elmRoot.LastChild.AppendChild(elmAllocation);
        elmRoot.LastChild.LastChild.AppendChild(txtAllocation);

        elmAllocation = docAllocation.CreateElement("PropertyCode");
        txtAllocation = docAllocation.CreateTextNode(PropertyCode);
        elmRoot.LastChild.AppendChild(elmAllocation);
        elmRoot.LastChild.LastChild.AppendChild(txtAllocation);

        elmAllocation = docAllocation.CreateElement("PropertyType");
        txtAllocation = docAllocation.CreateTextNode(PropertyType);
        elmRoot.LastChild.AppendChild(elmAllocation);
        elmRoot.LastChild.LastChild.AppendChild(txtAllocation);

        elmAllocation = docAllocation.CreateElement("ContractLength");
        txtAllocation = docAllocation.CreateTextNode(ContractLength);
        elmRoot.LastChild.AppendChild(elmAllocation);
        elmRoot.LastChild.LastChild.AppendChild(txtAllocation);

        elmAllocation = docAllocation.CreateElement("RentStartDate");
        txtAllocation =
		docAllocation.CreateTextNode(RentStartDate.ToString("d"));
        elmRoot.LastChild.AppendChild(elmAllocation);
        elmRoot.LastChild.LastChild.AppendChild(txtAllocation);

        elmAllocation = docAllocation.CreateElement("MonthlyRent");
        txtAllocation =
		docAllocation.CreateTextNode(MonthlyRent.ToString("F"));
        elmRoot.LastChild.AppendChild(elmAllocation);
        elmRoot.LastChild.LastChild.AppendChild(txtAllocation);

        docAllocation.Save(Filename);
        ShowRentalAllocations();
    }
}

Return to the Rental Allocation form and double-click the Close button

Implement the event as follows:

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

Access the Rent Payments form and double-click the New Rent Payment button

Implement the event as follows:

private void btnNewPayment_Click(object sender, EventArgs e)
{
    int ReceiptNumber;
    string AllocationCode,
           TenantAccountNumber, TenantName,
           PaymentFor, PropertyCode, PropertyType;
    DateTime DateReceived;
    double AmountReceived;

    RentPayment editor = new RentPayment();
    XmlDocument docPayment = new XmlDocument();
    Directory.CreateDirectory(@"C:\Solas Property Rental");
    string Filename = @"C:\Solas Property Rental\payments.xml";

    // If some payments were previously made
    if (File.Exists(Filename))
    {
        // Open the payments.xml file
        docPayment.Load(Filename);

        // Locate the root element
        XmlElement elmAllocation = docPayment.DocumentElement;
        // Get a list of the child nodes
        XmlNodeList lstAllocations = elmAllocation.ChildNodes;

        // Get the last receipt number
        ReceiptNumber =
            int.Parse(lstAllocations[lstAllocations.Count
                                    - 1].FirstChild.InnerText) + 1;

        editor.txtReceiptNumber.Text = ReceiptNumber.ToString();
    }
    else
    {
        // If no payment has ever been made,
        // create a new XML file for the payments
        docPayment.LoadXml("<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
                           "<RentPayments></RentPayments>");

        // We will start the receipt numbers at 101
        ReceiptNumber = 101;

        editor.txtReceiptNumber.Text = ReceiptNumber.ToString();
    }

    // Display the Rent Payment dialog box
    if (editor.ShowDialog() == DialogResult.OK)
    {
        // If the user had clicked OK,
        // Prepare the elements of the XML file
        ReceiptNumber = int.Parse(editor.txtReceiptNumber.Text);
        DateReceived = editor.dtpDateReceived.Value;
        AllocationCode = editor.txtAllocationCode.Text;
        TenantAccountNumber = editor.txtTenantAcntNber.Text;
        TenantName = editor.txtTenantName.Text;
        PropertyCode = editor.txtPropertyCode.Text;
        PropertyType = editor.txtPropertyType.Text;
        PaymentFor = editor.cbxMonths.Text + " " + editor.txtYear.Text;
        AmountReceived = double.Parse(editor.txtAmountReceived.Text);

        // Get a reference to the root element
        XmlElement elmRoot = docPayment.DocumentElement;
        // Create an element named Payment
        XmlElement elmPayment = docPayment.CreateElement("Payment");
        // Add the new element as the last node of the root element
        elmRoot.AppendChild(elmPayment);

        // Get a reference to the root element
        elmRoot = docPayment.DocumentElement;

        // Create an element
        elmPayment = docPayment.CreateElement("ReceiptNumber");
        // Create the value of the new element
        XmlText txtPayment = docPayment.CreateTextNode(ReceiptNumber.ToString());
        // Add the new element as a child of the Payment element
        elmRoot.LastChild.AppendChild(elmPayment);
        // Specify the value of the new element
        elmRoot.LastChild.LastChild.AppendChild(txtPayment);

	// Follow the same logic for the other elements

        elmPayment = docPayment.CreateElement("DateReceived");
        txtPayment = docPayment.CreateTextNode(DateReceived.ToString("d"));
        elmRoot.LastChild.AppendChild(elmPayment);
        elmRoot.LastChild.LastChild.AppendChild(txtPayment);

        elmPayment = docPayment.CreateElement("AllocationCode");
        XmlText txtAllocation = docPayment.CreateTextNode(AllocationCode);
        elmRoot.LastChild.AppendChild(elmPayment);
        elmRoot.LastChild.LastChild.AppendChild(txtAllocation);

        elmPayment = docPayment.CreateElement("TenantAccountNumber");
        txtAllocation = docPayment.CreateTextNode(TenantAccountNumber);
        elmRoot.LastChild.AppendChild(elmPayment);
        elmRoot.LastChild.LastChild.AppendChild(txtAllocation);

        elmPayment = docPayment.CreateElement("TenantName");
        txtAllocation = docPayment.CreateTextNode(TenantName);
        elmRoot.LastChild.AppendChild(elmPayment);
        elmRoot.LastChild.LastChild.AppendChild(txtAllocation);

        elmPayment = docPayment.CreateElement("PropertyCode");
        txtAllocation = docPayment.CreateTextNode(PropertyCode);
        elmRoot.LastChild.AppendChild(elmPayment);
        elmRoot.LastChild.LastChild.AppendChild(txtAllocation);

        elmPayment = docPayment.CreateElement("PropertyType");
        txtAllocation = docPayment.CreateTextNode(PropertyType);
        elmRoot.LastChild.AppendChild(elmPayment);
        elmRoot.LastChild.LastChild.AppendChild(txtAllocation);

        elmPayment = docPayment.CreateElement("PaymentFor");
        txtAllocation = docPayment.CreateTextNode(PaymentFor);
        elmRoot.LastChild.AppendChild(elmPayment);
        elmRoot.LastChild.LastChild.AppendChild(txtAllocation);

        elmPayment = docPayment.CreateElement("AmountReceived");
        txtAllocation = docPayment.CreateTextNode(AmountReceived.ToString("F"));
        elmRoot.LastChild.AppendChild(elmPayment);
        elmRoot.LastChild.LastChild.AppendChild(txtAllocation);

        docPayment.Save(Filename);
        ShowRentPayments();
    }
}

Return to the Rental Allocation form and double-click the Close button

Implement the event as follows:

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

Execute the application

Create the following Rental Allocations:

	Allocation 1	Allocation 2	Allocation 3	Allocation 4
Allocation Code	4205-8274	5920-9417	2792-4075	7957-7294
Date Allocated	8/12/2002	2/18/2004	3/24/2004	10/26/2007
Account #	24-68-84	57-97-15	19-38-84	20-48-46
Prop Code	726-454	625-936	371-801	727-768
Contract Length	12 Months	3 Months	12 Months	6 Months
Start Date	10/1/2002	4/1/2004	6/1/2004	2/1/2008

Create the following Rent Payments:

	Date Received	Allocation Code	Payment For		Amount
	Date Received	Allocation Code	Month	Year	Amount
Payment 1	10/25/2002	4205-8274	October	2002	1150.50
Payment 2	11/28/2002	4205-8274	November	2002	1150.50
Payment 3	4/28/2004	5920-9417	April	2004	1750.00
Payment 4	7/5/2004	2792-4075	June	2004	1250.25
Payment 5	6/3/2004	5920-9417	May	2004	1750.00
Payment 6	7/30/2004	2792-4075	July	2004	1250.25
Payment 7	7/5/2004	5920-9417	June	2004	1750.00
Payment 8	12/30/2002	4205-8274	December	2002	1150.50

Close the DOS window

Exercises

Solas Property Rental

Open the Solas Property Rental database from this lesson
Configure the Rental Allocations form so that, after the user has entered a property code and press Tab (or when the control looses focus), the database will first check the status of the property. If the property is occupied, a message box will be displayed to the user and that particular property cannot be selected (the property code text box should be set empty)
Configure the Rent Payments so that the user can decide to see only the payments for one particular tenant (you can create a contextual menu so that if the user right-clicks a certain row and click View Tenant's Payments, the list view would display only that tenant's payments. Of course, make sure the user has a way to display all payments again)


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