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INotifyPropertyChanged Interface

Notifies clients that a property value has changed.

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

public interface INotifyPropertyChanged
public interface INotifyPropertyChanged
public interface INotifyPropertyChanged
Not applicable.

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. If your data source implements the INotifyPropertyChanged and you are performing asynchronous operations you should not make changes to the data source on a background thread. Instead, you should read the data on a background thread and merge the data into a list on the UI thread.

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

	// This is the BindingSource used to bind 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.
		List<DemoCustomer> customerList = new List<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;
	}

	// This event handler changes the value of the CompanyName
	// property for the first item in the list.
	void changeItemBtn_Click(object sender, EventArgs e)
	{
		// Get a reference to the list from the BindingSource.
		List<DemoCustomer> customerList =
			this.customersBindingSource.DataSource as List<DemoCustomer>;

		// Change the value of the CompanyName property for the 
		// first item in the list.
		customerList[0].CompanyName = "Tailspin Toys";

	}

	

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

// This class implements a simple customer type 
// 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 customerName = String.Empty;
	private string companyNameValue = 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()
	{
		customerName = "no data";
		companyNameValue = "no data";
		phoneNumberValue = "no data";
	}

	// 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 CompanyName
	{
		get
		{
			return this.companyNameValue;
		}

		set
		{
            if (value != this.companyNameValue)
            {
                this.companyNameValue = value;
                NotifyPropertyChanged("CompanyName");
            }
		}
	}

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

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

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0

.NET Compact Framework

Supported in: 2.0

XNA Framework

Supported in: 1.0

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