title: iOS Modal Popup Starts Transparent But Turns Blank
body: <p>Using the iOS Simulator, I'm trying to get the modal to appear over the parent controller with a transparent background.  I define the controller as:</p>
  
  <pre><code>var controller = new DailyRewardController();
  
  controller.ModalPresentationStyle = UIModalPresentationStyle.CurrentContext;
  controller.View.BackgroundColor = UIColor.Clear;
  controller.View.Opaque = true;
  
  PresentViewController (controller, true, null);
  </code></pre>
  
  <p>The controller initially appears with a transparent background, but as the animation finishes, the screen is now black, as in the following screenshot.  Note: ignore the hideous popup; it's only a prototype :-)</p>
  
  <p><img src="https://i.stack.imgur.com/WAqhx.png" alt="enter image description here"></p>
  
  <p>This is how it appears after the animation finishes; however, as the animation runs, it's transparent...  Any idea why?</p>