RoutedPropertyChangedEventHandler<T> RoutedPropertyChangedEventHandler<T> RoutedPropertyChangedEventHandler<T> RoutedPropertyChangedEventHandler<T> Delegate

Definition

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

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
T

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

Parameters
sender

The object where the event handler is attached.

e

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

Inheritance
RoutedPropertyChangedEventHandler<T>RoutedPropertyChangedEventHandler<T>RoutedPropertyChangedEventHandler<T>RoutedPropertyChangedEventHandler<T>

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.

Applies to

See Also