Notifies clients that a property value has changed.
Namespace: System.ComponentModel
Assembly: System (in system.dll)
Visual Basic (Declaration)
Public Interface INotifyPropertyChanged
Dim instance As INotifyPropertyChanged
public interface INotifyPropertyChanged
public interface class INotifyPropertyChanged
public interface INotifyPropertyChanged
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. 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:
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.
Imports System
Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Data
Imports System.Data.Common
Imports System.Diagnostics
Imports System.Drawing
Imports System.Data.SqlClient
Imports 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
Inherits System.Windows.Forms.Form
' This button causes the value of a list element to be changed.
Private changeItemBtn As New Button()
' This is the DataGridView control that displays the contents
' of the list.
Private customersDataGridView As New DataGridView()
' This is the BindingSource used to bind the list to the
' DataGridView control.
Private customersBindingSource As New BindingSource()
Public Sub New()
' Set up the "Change Item" button.
Me.changeItemBtn.Text = "Change Item"
Me.changeItemBtn.Dock = DockStyle.Bottom
AddHandler Me.changeItemBtn.Click, AddressOf changeItemBtn_Click
Me.Controls.Add(Me.changeItemBtn)
' Set up the DataGridView.
customersDataGridView.Dock = DockStyle.Top
Me.Controls.Add(customersDataGridView)
Me.Size = New Size(800, 200)
AddHandler Me.Load, AddressOf Form1_Load
End Sub 'New
Private Sub Form1_Load(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles Me.Load
' Create and populate the list of DemoCustomer objects
' which will supply data to the DataGridView.
Dim customerList As New List(Of DemoCustomer)
customerList.Add(DemoCustomer.CreateNewCustomer())
customerList.Add(DemoCustomer.CreateNewCustomer())
customerList.Add(DemoCustomer.CreateNewCustomer())
' Bind the list to the BindingSource.
Me.customersBindingSource.DataSource = customerList
' Attach the BindingSource to the DataGridView.
Me.customersDataGridView.DataSource = Me.customersBindingSource
End Sub 'Form1_Load
' This event handler changes the value of the CompanyName
' property for the first item in the list.
Private Sub changeItemBtn_Click(ByVal sender As Object, ByVal e As EventArgs)
' Get a reference to the list from the BindingSource.
Dim customerList As List(Of DemoCustomer) = _
CType(customersBindingSource.DataSource, List(Of DemoCustomer))
' Change the value of the CompanyName property for the
' first item in the list.
customerList(0).CompanyName = "Tailspin Toys"
End Sub
<STAThread()> _
Shared Sub Main()
Application.EnableVisualStyles()
Application.Run(New Form1())
End Sub
End Class
' This class implements a simple customer type
' that implements the IPropertyChange interface.
Public Class DemoCustomer
Implements INotifyPropertyChanged
' These fields hold the values for the public properties.
Private idValue As Guid = Guid.NewGuid()
Private customerName As String = String.Empty
Private companyNameValue As String = String.Empty
Private phoneNumberValue As String = String.Empty
Public Event PropertyChanged As PropertyChangedEventHandler _
Implements INotifyPropertyChanged.PropertyChanged
Private Sub NotifyPropertyChanged(ByVal info As String)
RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(info))
End Sub
' The constructor is private to enforce the factory pattern.
Private Sub New()
customerName = "no data"
companyNameValue = "no data"
phoneNumberValue = "no data"
End Sub
' This is the public factory method.
Public Shared Function CreateNewCustomer() As DemoCustomer
Return New DemoCustomer()
End Function
' This property represents an ID, suitable
' for use as a primary key in a database.
Public ReadOnly Property ID() As Guid
Get
Return Me.idValue
End Get
End Property
Public Property CompanyName() As String
Get
Return Me.companyNameValue
End Get
Set(ByVal value As String)
If Not (value = companyNameValue) Then
Me.companyNameValue = value
NotifyPropertyChanged("CompanyName")
End If
End Set
End Property
Public Property PhoneNumber() As String
Get
Return Me.phoneNumberValue
End Get
Set(ByVal value As String)
If Not (value = phoneNumberValue) Then
Me.phoneNumberValue = value
NotifyPropertyChanged("PhoneNumber")
End If
End Set
End Property
End Class
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