title: Update WritableBitmap after Image.Source has been set
body: <p>I am trying to use <code>WritableBitmap</code> to do some pixel level manipulation of bitmap images.But i can't get it working.What i want to do is manipulating pixel data of <code>WritableBitmap</code> after i assign <code>Image.Source</code> property with my bitmap.I googled and the only thing i found is call to <code>bitmap.Invalidate()</code> method but it seems to be deprecated as i couldn't find that method in <code>WritableBitmap</code> class.following is the code i am using to get the image updated but no luck:</p>
  
  <pre><code>    wbitmap.Lock();
      wbitmap.WritePixels(rect, pixels, stride, 0);
      wbitmap.AddDirtyRect(new Int32Rect(0, 0, width, height));
      wbitmap.Unlock();
  
      //given that i've already assigned image.Source with "wbitmap"
      image.InvalidateVisual();
  </code></pre>
  
  <p>any thoughts on this?</p>
  
  <p><strong>EDIT</strong></p>
  
  <p>i would appreciate any suggestion for other way of <strong>FAST</strong> 2D drawing in WPF better that <code>WritableBitmap</code>.</p>