This documentation is archived and is not being maintained.

AutomationPropertyChangedEventHandler Delegate

Represents the method implemented by the UI Automation client application to handle the event raised by a UI Automation provider when a property has changed.

Namespace:  System.Windows.Automation
Assembly:  UIAutomationTypes (in UIAutomationTypes.dll)

'Declaration
Public Delegate Sub AutomationPropertyChangedEventHandler ( _
	sender As Object, _
	e As AutomationPropertyChangedEventArgs _
)
'Usage
Dim instance As New AutomationPropertyChangedEventHandler(AddressOf HandlerMethod)

Parameters

sender
Type: System.Object

The object that raised the event.

e
Type: System.Windows.Automation.AutomationPropertyChangedEventArgs

Information about the event.

The AutomationElement represented by sender might not have any cached properties or patterns, depending on whether the application subscribed to this event while a CacheRequest was active.

Depending on the provider implementation, a property-changed event does not necessarily signify that the property value is different; it might just mean that the property was set, even to the same value. If your application needs to respond only to actual changes, it is your responsibility to track the state of the property.

In the following example, changes in the IsEnabled property of subscribed elements are handled.

Dim propChangeHandler As AutomationPropertyChangedEventHandler

''' <summary> 
''' Adds a handler for property-changed event; in particular, a change in the enabled state. 
''' </summary> 
''' <param name="element">The UI Automation element whose state is being monitored.</param> 
Public Sub SubscribePropertyChange(ByVal element As AutomationElement)
    propChangeHandler = _
        New AutomationPropertyChangedEventHandler(AddressOf OnPropertyChange)
    Automation.AddAutomationPropertyChangedEventHandler(element, TreeScope.Element, _
        propChangeHandler, AutomationElement.IsEnabledProperty)

End Sub 'SubscribePropertyChange



''' <summary> 
''' Handler for property changes. 
''' </summary> 
''' <param name="src">The source whose properties changed.</param> 
''' <param name="e">Event arguments.</param> 
Private Sub OnPropertyChange(ByVal src As Object, ByVal e As AutomationPropertyChangedEventArgs) 
    Dim sourceElement As AutomationElement = DirectCast(src, AutomationElement)
    If e.Property Is AutomationElement.IsEnabledProperty Then 
        Dim enabled As Boolean = CBool(e.NewValue)
        ' TODO: Do something with the new value.  
        ' The element that raised the event can be identified by its runtime ID property. 
    Else 
    End If 
 ' TODO: Handle other property-changed events. 
End Sub 'OnPropertyChange


Public Sub UnsubscribePropertyChange(ByVal element As AutomationElement)
    If (propChangeHandler IsNot Nothing) Then
        Automation.RemoveAutomationPropertyChangedEventHandler(element, propChangeHandler)
    End If 

End Sub 'UnsubscribePropertyChange

Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003

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
Show: