title: Make WPF Image load async
body: <p>I would like to load Gravatar-Images and set them from code behind to a WPF Image-Control.
  So the code looks like </p>
  
  <pre><code>imgGravatar.Source = GetGravatarImage(email);
  </code></pre>
  
  <p>Where GetGravatarImage looks like:</p>
  
  <pre><code>BitmapImage bi = new BitmapImage();
  bi.BeginInit();
  bi.UriSource = new Uri( GravatarImage.GetURL( "http://www.gravatar.com/avatar.php?gravatar_id=" + email) , UriKind.Absolute );
  bi.EndInit();
  return bi;
  </code></pre>
  
  <p>Unfortunately this locks the GUI when the network connection is slow. Is there a way to assign the image-source and let it load the image in the background without blocking the UI?</p>
  
  <p>Thanks!</p>