Why is TriggerAction internal?

Is there ans good reason why the TriggerEvent class usd in EventTriggers is implemented internal? I can find 3 implementations of this abstract base Claas. One to play a sound and two different actions regarding storyboards. What if I want to have a "SendEmail" action? Is more 开发者_如何学Ca hypothetical question. I don't have n actual application for it. I just noticed it and was wondering why it is implemented this way. To me it would be logical to derive my own action and just use it in the event trigger (an interface would be even better). Am I missing a point here?

Regards!

I doubt that you can do anything with those classes, use Interactivity from the Blend SDK instead, which provides classes (TriggerAction<T> for example) that can be sub-classed.

Edit: Somehow this is only found in the Silverlight documentation of the class:

TriggerAction exists in Silverlight for WPF compatibility. TriggerAction is not intended to be derived from as a base for other trigger implementations; the entire Triggers syntax is a discouraged technique in Silverlight 4. For more information, see Remarks in EventTrigger, or Customizing the Appearance of an Existing Control by Using a ControlTemplate.

Still no reason though.