title: How to set the background to transparent on a DialogViewController
body: <p>When I set the MonoTouch.Dialog background color to uiclear(transparent), it throw an exception, why? and How to set it to transparent.</p>
  
  <blockquote>
    <p>Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object MyDialogViewController.LoadView () [0x00016] in  MyDialogViewController.cs:          ParentViewController.View.BackgroundColor = UIColor.Clear</p>
  </blockquote>
  
  <pre><code>public class MyDialogViewController: DialogViewController
  {
      public MyDialogViewController (RootElement root)  : base (root) 
      {
      }
  
      public override void LoadView() 
      {
          base.LoadView ();
          this.TableView.BackgroundColor = UIColor.Clear;
      ParentViewController.View.BackgroundColor = UIColor.Clear;
  
      }
  }
  
  
      public void xxxxx(){
        var menu = new RootElement(""){
              new Section ("Demo"){
                  new EntryElement("Name", "",""),
              },
          };
  
          var menuDVC = new MyDialogViewController (menu) {
              Autorotate = true
          };
  
  
  
          this.View.AddSubview(menuDVC.View);
  }
  </code></pre>