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How to: Create a Custom Routed Event

For your custom event to support event routing, you need to register a RoutedEvent using the RegisterRoutedEvent method. This example demonstrates the basics of creating a custom routed event.

As shown in the following example, you first register a RoutedEvent using the RegisterRoutedEvent method. By convention, the RoutedEvent static field name should end with the suffix Event. In this example, the name of the event is Tap and the routing strategy of the event is Bubble. After the registration call, you can provide add-and-remove common language runtime (CLR) event accessors for the event.

Note that even though the event is raised through the OnTap virtual method in this particular example, how you raise your event or how your event responds to changes depends on your needs.

Note also that this example basically implements an entire subclass of Button; that subclass is built as a separate assembly and then instantiated as a custom class on a separate Extensible Application Markup Language (XAML) page. This is to illustrate the concept that subclassed controls can be inserted into trees composed of other controls, and that in this situation, custom events on these controls have the very same event routing capabilities as any native Windows Presentation Foundation (WPF) element does.

Public Class MyButtonSimple
    Inherits Button

    ' Create a custom routed event by first registering a RoutedEventID 
    ' This event uses the bubbling routing strategy 
    Public Shared ReadOnly TapEvent As RoutedEvent = EventManager.RegisterRoutedEvent("Tap", RoutingStrategy.Bubble, GetType(RoutedEventHandler), GetType(MyButtonSimple))

    ' Provide CLR accessors for the event 
    Public Custom Event Tap As RoutedEventHandler
        AddHandler(ByVal value As RoutedEventHandler)
            Me.AddHandler(TapEvent, value)
        End AddHandler 

        RemoveHandler(ByVal value As RoutedEventHandler)
            Me.RemoveHandler(TapEvent, value)
        End RemoveHandler 

        RaiseEvent(ByVal sender As Object, ByVal e As RoutedEventArgs)
        End RaiseEvent 
    End Event 

    ' This method raises the Tap event 
    Private Sub RaiseTapEvent()
        Dim newEventArgs As New RoutedEventArgs(MyButtonSimple.TapEvent)
    End Sub 

    ' For demonstration purposes we raise the event when the MyButtonSimple is clicked 
    Protected Overrides Sub OnClick()
    End Sub 

End Class

      <Style TargetType="{x:Type custom:MyButtonSimple}">
        <Setter Property="Height" Value="20"/>
        <Setter Property="Width" Value="250"/>
        <Setter Property="HorizontalAlignment" Value="Left"/>
        <Setter Property="Background" Value="#808080"/>
    <StackPanel Background="LightGray">
	    <custom:MyButtonSimple Name="mybtnsimple" Tap="TapHandler">Click to see Tap custom event work</custom:MyButtonSimple>

Tunneling events are created the same way, but with RoutingStrategy set to Tunnel in the registration call. By convention, tunneling events in WPF are prefixed with the word "Preview".

To view the complete sample, including the implementation of the actual "Tap" event handler, see Custom Routed Events Sample. To see an example of how bubbling events work, see How to: Handle a Routed Event.

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