title: How to clear a WriteableBitmap
body: <p>I have a WriteableBitmap which I would like to repeatedly clear and redraw.</p>
  
  <p>I have seen references to writing to the Pixels array directly, but the Pixels array is not accessible in WriteableBitmap. I have also tried the suggestion of recreating the WriteableBitmap each time, but my app runs out of memory almost immediately.</p>
  
  <p>Is there a simple way to clear a WriteableBitmap?</p>