防止子控件接收路由事件

Question

Lets say I have my user-control somewhere in the visual tree. Parent and children are 3rd-party controls that I cannot modify. I want to filter keyboard events in my control so that children controls do not receive some keyboard events, but the parent controls do.

I'll try to explain what I want to achieve with some diagrams. If controls do not handle keyboard events, all events bounce through the visual tree:

But, fe when user presses A ,

1. Child2.OnPreviewKeyDown() should NOT be called
2. but Parent2.OnTextInput should still receive an event

I can achive (1) by setting e.Handled = true in MyControl.PreviewKeyDown . The problem is that in this case TextInput event is not generated:

Is there a way to achieve behavior like on the 2nd picture?

Added: The problem I'm trying to solve is that a 3rd-party control (Child 2) steals some input in OnPreviewKeyDown (and marks event as handled), and I'm trying to avoid that.

Answer 1

What you can generally do in WPF to handle a suppressed event is add a handler in code and re-raise the event. To do this, you use the UIElement.AddHandler() method, for example:

child2.AddHandler(UIElement.TextInput, new TextCompositionEventHandler(nameOfYourHandlerFunction), true);

The 'true' boolean value is what makes nameOfYourHandlerFunction fire even if the Handled flag is set. The event won't automatically re-bubble by doing that, so you need to raise the event again.

base.RaiseEvent(e);

This works for events that have a routing strategy of Bubble.