RoutedPropertyChangedEventHandler<T> Delegate

Definition

generic <typename T>
public delegate void RoutedPropertyChangedEventHandler(System::Object ^ sender, RoutedPropertyChangedEventArgs<T> ^ e);

public delegate void RoutedPropertyChangedEventHandler<T>(object sender, RoutedPropertyChangedEventArgs<T> e);

type RoutedPropertyChangedEventHandler<'T> = delegate of obj * RoutedPropertyChangedEventArgs<'T> -> unit

Public Delegate Sub RoutedPropertyChangedEventHandler(Of T)(sender As Object, e As RoutedPropertyChangedEventArgs(Of T))

Type Parameters

Parameters

Examples

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

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

Slider childrenCountSlider = (Slider)LogicalTreeHelper.FindLogicalNode(myWindow, "ChildrenCountSlider");
childrenCountSlider.ValueChanged += new RoutedPropertyChangedEventHandler<double>(OnChildrenCountChanged);

Dim childrenCountSlider As Slider = CType(LogicalTreeHelper.FindLogicalNode(myWindow, "ChildrenCountSlider"), Slider)
AddHandler childrenCountSlider.ValueChanged, AddressOf OnChildrenCountChanged

private void OnChildrenCountChanged(object sender, RoutedPropertyChangedEventArgs<double> e)
{
 int childrenCount = (int)Math.Floor(e.NewValue + 0.5);

 // Update the children count...
 AutoIndexingGrid g = (AutoIndexingGrid)LogicalTreeHelper.FindLogicalNode(myWindow, "TargetGrid");
 while (g.Children.Count < childrenCount)
 {
 Control c = new Control();
 g.Children.Add(c);
 c.Style = (Style)c.FindResource("ImageWithBorder");
 }
 while (g.Children.Count > childrenCount)
 {
 g.Children.Remove(g.Children[g.Children.Count - 1]);
 }


 // Update TextBlock element displaying the count...
 TextBlock t = (TextBlock)LogicalTreeHelper.FindLogicalNode(myWindow, "ChildrenCountDisplay");
 t.Text = childrenCount.ToString();
}

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.

Remarks

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

See also

• RoutedPropertyChangedEventArgs<T>