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INotifyPropertyChanged Interface

Updated: January 2010

Notifies clients that a property value has changed.

Namespace:  System.ComponentModel
Assembly:  System (in System.dll)

public interface INotifyPropertyChanged

The INotifyPropertyChanged interface is used to notify clients, typically binding clients, that a property value has changed.

For example, consider a Person object with a property called FirstName. To provide generic property-change notification, the Person type implements the INotifyPropertyChanged interface and raises a PropertyChanged event when FirstName is changed.

For change notification to occur in a binding between a bound client and a data source, your bound type should either:

  • Implement the INotifyPropertyChanged interface (preferred).

  • Provide a change event for each property of the bound type.

Do not do both.

The following code example demonstrates the how to implement the INotifyPropertyChanged interface. When you run this example, you will notice the bound DataGridView control reflects the change in the data source without requiring the binding to be reset.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Data.Common;
using System.Diagnostics;
using System.Drawing;
using System.Data.SqlClient;
using System.Windows.Forms;

// This form demonstrates using a BindingSource to bind 
// a list to a DataGridView control. The list does not 
// raise change notifications, however the DemoCustomer type  
// in the list does. 
public class Form1 : System.Windows.Forms.Form
{
    // This button causes the value of a list element to be changed. 
    private Button changeItemBtn = new Button();

    // This DataGridView control displays the contents of the list. 
    private DataGridView customersDataGridView = new DataGridView();

    // This BindingSource binds the list to the DataGridView control. 
    private BindingSource customersBindingSource = new BindingSource();

    public Form1()
    {
        // Set up the "Change Item" button.
        this.changeItemBtn.Text = "Change Item";
        this.changeItemBtn.Dock = DockStyle.Bottom;
        this.changeItemBtn.Click +=
            new EventHandler(changeItemBtn_Click);
        this.Controls.Add(this.changeItemBtn);

        // Set up the DataGridView.
        customersDataGridView.Dock = DockStyle.Top;
        this.Controls.Add(customersDataGridView);

        this.Size = new Size(800, 200);
        this.Load += new EventHandler(Form1_Load);
    }

    private void Form1_Load(System.Object sender, System.EventArgs e)
    {
        // Create and populate the list of DemoCustomer objects 
        // which will supply data to the DataGridView.
        BindingList<DemoCustomer> customerList = new BindingList<DemoCustomer>();
        customerList.Add(DemoCustomer.CreateNewCustomer());
        customerList.Add(DemoCustomer.CreateNewCustomer());
        customerList.Add(DemoCustomer.CreateNewCustomer());

        // Bind the list to the BindingSource. 
        this.customersBindingSource.DataSource = customerList;

        // Attach the BindingSource to the DataGridView. 
        this.customersDataGridView.DataSource =
            this.customersBindingSource;
    }

    // Change the value of the CompanyName property for the first  
    // item in the list when the "Change Item" button is clicked.
    void changeItemBtn_Click(object sender, EventArgs e)
    {
        // Get a reference to the list from the BindingSource.
        BindingList<DemoCustomer> customerList =
            this.customersBindingSource.DataSource as BindingList<DemoCustomer>;

        // Change the value of the CompanyName property for the  
        // first item in the list.
        customerList[0].CustomerName = "Tailspin Toys";
        customersBindingSource.ResetItem(0);
    }

    [STAThread]
    static void Main()
    {
        Application.EnableVisualStyles();
        Application.Run(new Form1());
    }
}

// This is a simple customer class that  
// implements the IPropertyChange interface. 
public class DemoCustomer  : INotifyPropertyChanged
{
    // These fields hold the values for the public properties. 
    private Guid idValue = Guid.NewGuid();
    private string customerNameValue = String.Empty;
    private string phoneNumberValue = String.Empty;

    public event PropertyChangedEventHandler PropertyChanged;

    private void NotifyPropertyChanged(String info)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(info));
        }
    }

    // The constructor is private to enforce the factory pattern. 
    private DemoCustomer()
    {
        customerNameValue = "Customer";
        phoneNumberValue = "(555)555-5555";
    }

    // This is the public factory method. 
    public static DemoCustomer CreateNewCustomer()
    {
        return new DemoCustomer();
    }

    // This property represents an ID, suitable 
    // for use as a primary key in a database. 
    public Guid ID
    {
        get
        {
            return this.idValue;
        }
    }

    public string CustomerName
    {
        get
        {
            return this.customerNameValue;
        }

        set
        {
            if (value != this.customerNameValue)
            {
                this.customerNameValue = value;
                NotifyPropertyChanged("CustomerName");
            }
        }
    }

    public string PhoneNumber
    {
        get
        {
            return this.phoneNumberValue;
        }

        set
        {
            if (value != this.phoneNumberValue)
            {
                this.phoneNumberValue = value;
                NotifyPropertyChanged("PhoneNumber");
            }
        }
    }
}

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0

.NET Compact Framework

Supported in: 3.5, 2.0

XNA Framework

Supported in: 3.0, 2.0, 1.0

Date

History

Reason

January 2010

Removed incorrect remark.

Content bug fix.

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