title: No events passed to WPF adorner layer
body: <p>I am trying to make a nice "drag and drop zone" in WPF that is displayed in the adorner layer when something is being dragged into the main application. The problem is that I do not get any events from my adorner, even though it according to documentation should receive all input events since it is in a higher z-order.</p>
  
  <p>To debug my problem I created a really simple example where I have a user control with only a button in it. This user control is displayed in the adorner layer, but I cannot click the button. Why? What have I done wrong?</p>
  
  <p>My adorner class is constructed like this:</p>
  
  <pre><code>    public ShellOverlayAdorner(UIElement element, AdornerLayer adornerLayer)
          :base(element)
      {
          _adornerLayer = adornerLayer;
  
          _overlayView = new AdornedElement();
          _overlayView.AllowDrop = true;
          _adornerLayer.Add(this);
       }
  </code></pre>
  
  <p>and is created in the main window by </p>
  
  <pre><code>    private void Window_Loaded(object sender, RoutedEventArgs e)
      {
          adornerLayer = AdornerLayer.GetAdornerLayer(MyTopGridWithButtonInIt);
          ShellOverlayAdorner shell = new ShellOverlayAdorner(MyTopGridWithButtonInIt, adornerLayer);
  
      }
  </code></pre>
  
  <p>I do not get any events at all from my control, i.e. no mouse clicks, mouse over, button clicks. I cannot even click the button in the adorner layer. What have I done wrong?</p>