silverlight bug?

I need your help!

I have some usercontrol in which hovering mouse on this keyword threw an strange error

class Puzzle : UserControl {

 public void Animate()
 {
        this.SetValue(Canvas开发者_如何学C.TopProperty, 0.0); // expression has been evaluated and has no value

  }   
}

what is wrong with this approach?

From your followup comment, you are trying to watch a method call on a method that has a void return type.

The debugger is trying to be helpful by telling you it has no value.

Try adding a watch on the matching GetValue method instead :)