How to: Implement Property Change Notification
To support OneWay or TwoWay binding to enable your binding target properties to automatically reflect the dynamic changes of the binding source (for example, to have the preview pane updated automatically when the user edits a form), your class needs to provide the proper property changed notifications. This example shows how to create a class that implements INotifyPropertyChanged.
Example
To implement INotifyPropertyChanged you need to declare the PropertyChanged event and create the OnPropertyChanged method. Then for each property you want change notifications for, you call OnPropertyChanged whenever the property is updated.
using System.ComponentModel;
namespace SDKSample
{
// This class implements INotifyPropertyChanged
// to support one-way and two-way bindings
// (such that the UI element updates when the source
// has been changed dynamically)
public class Person : INotifyPropertyChanged
{
private string name;
// Declare the event
public event PropertyChangedEventHandler PropertyChanged;
public Person()
{
}
public Person(string value)
{
this.name = value;
}
public string PersonName
{
get { return name; }
set
{
name = value;
// Call OnPropertyChanged whenever the property is updated
OnPropertyChanged("PersonName");
}
}
// Create the OnPropertyChanged method to raise the event
protected void OnPropertyChanged(string name)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(name));
}
}
}
}
Imports System.ComponentModel
' This class implements INotifyPropertyChanged
' to support one-way and two-way bindings
' (such that the UI element updates when the source
' has been changed dynamically)
Public Class Person
Implements INotifyPropertyChanged
Private personName As String
Sub New()
End Sub
Sub New(ByVal Name As String)
Me.personName = Name
End Sub
' Declare the event
Public Event PropertyChanged As PropertyChangedEventHandler Implements INotifyPropertyChanged.PropertyChanged
Public Property Name() As String
Get
Return personName
End Get
Set(ByVal value As String)
personName = value
' Call OnPropertyChanged whenever the property is updated
OnPropertyChanged("Name")
End Set
End Property
' Create the OnPropertyChanged method to raise the event
Protected Sub OnPropertyChanged(ByVal name As String)
RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(name))
End Sub
End Class
To see an example of how the Person class can be used to support TwoWay binding, see How to: Control When the TextBox Text Updates the Source.
For the complete sample, see Simple Binding Sample.
See Also
Concepts
Binding Sources Overview
Data Binding Overview