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INotifyPropertyChanged Interface

Notifies clients that a property value has changed.

Namespace:  System.ComponentModel
Assemblies:   System (in System.dll)
  System.ObjectModel (in System.ObjectModel.dll)

'Declaration
Public Interface INotifyPropertyChanged

The INotifyPropertyChanged type exposes the following members.

  NameDescription
Public eventSupported by the XNA FrameworkSupported by Portable Class LibrarySupported in .NET for Windows Store appsPropertyChangedOccurs when a property value changes.
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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.

If you use the CallerMemberName attribute, calls to the NotifyPropertyChanged method don't have to specify the property name as a string argument. For more information, see Caller Information (C# and Visual Basic).

Imports System
Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Drawing
Imports System.Runtime.CompilerServices
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()
        InitializeComponent()

        ' 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(400, 200)
    End Sub 

    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)

        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 

    ' 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"
        customerList(0).PhoneNumber = "(708)555-0150" 
    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

    ' This method is called by the Set accessor of each property. 
    ' The CallerMemberName attribute that is applied to the optional propertyName 
    ' parameter causes the property name of the caller to be substituted as an argument. 
    Private Sub NotifyPropertyChanged(<CallerMemberName()> Optional ByVal propertyName As String = Nothing)
        RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(propertyName))
    End Sub 

    ' The constructor is private to enforce the factory pattern. 
    Private Sub New()
        customerNameValue = "Customer"
        phoneNumberValue = "(312)555-0100" 
    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 CustomerName() As String 
        Get 
            Return Me.customerNameValue
        End Get 

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

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

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