title: DrawingSurface Draw event does not fire
body: <p>I'm working on a Silverlight application and am trying to use 3D support in my app. I have enabled 3D support with this line:</p>
  
  <pre><code>&lt;param name="enableGPUAcceleration" value="true" /&gt;
  </code></pre>
  
  <p>Also, the application is running on localhost:80 via IIS and this has permission for 3D usage set to Allow.</p>
  
  <p>I have a DrawingSurface in a xaml page and attached its Draw event in which I simply clear the surface to red. The Draw does not fire. So I tried invalidating the DrawingSurface on MouseLeftButtonDown. Here's some code:</p>
  
  <pre><code>        private void TestDrawing_Draw(object sender, System.Windows.Controls.DrawEventArgs e)
      {
          GraphicsDeviceManager.Current.GraphicsDevice.Clear(new Microsoft.Xna.Framework.Color(255, 0, 0));
      }
  
      private void TestDrawing_MouseLeftButtonDown(object sender, System.Windows.Input.MouseButtonEventArgs e)
      {
          if (GraphicsDeviceManager.Current.RenderMode == RenderMode.Hardware)
          {
              TestDrawing.Invalidate();
          }
      }
  </code></pre>
  
  <p>Checking in debugmode, I find that the MouseLeftButtonDown event does fire. The GraphicsDeviceManager.Current.RenderMode is set to RenderMode.Hardware and the Invalidate() method is executed. But, the Draw event still does not fire.</p>
  
  <p>I've created a testproject which runs via a Developer server on a specific port (50814). Again, enableGPUAcceleration is set to true and permission has been set to Allow. This testproject does fire the Draw event.</p>
  
  <p>So... my large application, running on an IIS server (localhost:80) with enableGPUAcceleration set to true and permission set to Allow does not fire the Draw event. A simple testproject running a Developer server on port 50814 with enableGPUAcceleration set to true and permission to Allow does fire the Draw event.</p>
  
  <p>I've no idea how to enable 3D for my application. Do you guys have any suggestions?!</p>