wpfxamlf#handlerroutedevent

F# Event Handler using XAML markup


Now that I have a Custom Routed Event, how can I specify a handler in XAML?

<Window.Resources>
    <Style TargetType="Grid">
        <Setter Property="funk:Tap.Handler"
                Value="{Binding TapHandler}"/>
    </Style>
</Window.Resources>

Allowing:


Solution

  • Using an Attached Property (based on this post)

    type Tap() =
        inherit DependencyObject()
    
        // For easy exchange
        static let routedEvent = MyButtonSimple.TapEvent
    
        static let HandlerProperty =
            DependencyProperty.RegisterAttached
                ( "Handler", typeof<RoutedEventHandler>, 
                    typeof<Tap>, new PropertyMetadata(null))
    
        static let OnEvent (sender : obj) args = 
            let control = sender :?> UIElement
            let handler = control.GetValue(HandlerProperty) :?> RoutedEventHandler
            if not <| ((handler, null) ||> LanguagePrimitives.PhysicalEquality) then
                handler.Invoke(sender, args)
    
        static do EventManager.RegisterClassHandler(
                    typeof<FrameworkElement>, routedEvent, 
                        RoutedEventHandler(OnEvent))
    
        static member GetHandler (element: UIElement) : RoutedEventHandler = 
            element.GetValue(HandlerProperty) :?> _
    
        static member SetHandler (element: UIElement, value : RoutedEventHandler) = 
            element.SetValue(HandlerProperty, value)
    

    wpfApp demo files can be found here (FsXaml 2.1.0)