title: Drawing Control Visual Elements onto a Rectangle
body: <p>I've got a custom composite WPF control (AvalonEdit) in my application that I'd like to animate whenever its Text property is changed. What I intend to do is:</p>
  
  <ol>
  <li>Create a copy of the control's visual representation before the text is changed and paint it over a rectangle.</li>
  <li>Fade out the above rectangle, update the text property and fade in the control using the DoubleAnimation and Storyboard classes.</li>
  </ol>
  
  <p>I've got #2 figured out but haven't got a clue about how I'd achieve #1. Any help would be appreciated.</p>