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RoutedPropertyChangedEventHandler(Of T) Delegate

Represents methods that will handle various routed events that track property value changes.

Namespace:  System.Windows
Assembly:  PresentationFramework (in PresentationFramework.dll)

'Declaration
Public Delegate Sub RoutedPropertyChangedEventHandler(Of T) ( _
	sender As Object, _
	e As RoutedPropertyChangedEventArgs(Of T) _
)

Type Parameters

T

The type of the property value where changes in value are reported.

Parameters

sender
Type: System.Object

The object where the event handler is attached.

e
Type: System.Windows.RoutedPropertyChangedEventArgs(Of T)

The event data. Specific event definitions will constrain RoutedPropertyChangedEventArgs(Of T) to a type, with the type parameter of the constraint matching the type parameter constraint of a delegate implementation.

Examples of events that use type-constrained delegates based on RoutedPropertyChangedEventHandler(Of T) include TreeView.SelectedItemChanged and RangeBase.ValueChanged.

The following example defines and attaches a handler method for the ValueChanged event.

The handler is based on RoutedPropertyChangedEventHandler(Of T), and is defined in the second segment of the code example, with the type parameter of the generic constrained to Double.

			Dim childrenCountSlider As Slider = CType(LogicalTreeHelper.FindLogicalNode(myWindow, "ChildrenCountSlider"), Slider)
			AddHandler childrenCountSlider.ValueChanged, AddressOf OnChildrenCountChanged
		Private Sub OnChildrenCountChanged(ByVal sender As Object, ByVal e As RoutedPropertyChangedEventArgs(Of Double))
			Dim childrenCount As Integer = CInt(Fix(Math.Floor(e.NewValue + 0.5)))

			'  Update the children count...
			Dim g As AutoIndexingGrid = CType(LogicalTreeHelper.FindLogicalNode(myWindow, "TargetGrid"), AutoIndexingGrid)
			Do While g.Children.Count < childrenCount
				Dim c As New Control()
				g.Children.Add(c)
				c.Style = CType(c.FindResource("ImageWithBorder"), Style)
			Loop
			Do While g.Children.Count > childrenCount
				g.Children.Remove(g.Children(g.Children.Count - 1))
			Loop


			'  Update TextBlock element displaying the count...
			Dim t As TextBlock = CType(LogicalTreeHelper.FindLogicalNode(myWindow, "ChildrenCountDisplay"), TextBlock)
			t.Text = childrenCount.ToString()
		End Sub

This particular example does not use the routed-event characteristic of the event; the event is handled on the same element that it is raised on. This is not always the case. For a routed event, it is possible that the source of the event is a different object than the object where the handler is attached.

.NET Framework

Supported in: 4.5, 4, 3.5, 3.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

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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