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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
Dim instance As 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.

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 DataGridView control displays the contents of the list. 
    Private customersDataGridView As New DataGridView()

    ' This BindingSource binds 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

        ' Set up the DataGridView.
        customersDataGridView.Dock = DockStyle.Top

        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 BindingList(Of DemoCustomer)


        ' 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 BindingList(Of DemoCustomer) = _
            CType(customersBindingSource.DataSource, BindingList(Of DemoCustomer))

        ' Change the value of the CompanyName property for the  
        ' first item in the list.
        customerList(0).CustomerName = "Tailspin Toys" 

    End Sub

    <STAThread()> _
    Shared Sub Main()
        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 customerNameValue 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()
        customerNameValue = "Customer"
        phoneNumberValue = "(555)555-5555" 

    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
            Return Me.idValue
        End Get 
    End Property 

    Public Property CustomerName() As String 
            Return Me.customerNameValue
        End Get 

        Set(ByVal value As String)
            If Not (value = customerNameValue) Then 
                Me.customerNameValue = value
            End If 
        End Set 
    End Property 

    Public Property PhoneNumber() As String 
            Return Me.phoneNumberValue
        End Get 

        Set(ByVal value As String)
            If Not (value = phoneNumberValue) Then 
                Me.phoneNumberValue = value
            End If 

        End Set 
    End Property 
End Class

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




January 2010

Removed incorrect remark.

Content bug fix.