title: Monotouch open document - UIDocumentInterationController
body: <p>I want to open a document on my iphone app written in monotouch
   - i.e. launch a PDF file in the default PDF viewer.</p>
  
  <p>I think I should be using UIDocumentInterationController?</p>
  
  <p>Anyone have any Ideas on this.. </p>
  
  <p>I have put together the following on a viewcontroller ( with a toolbar)  </p>
  
  <p>but it doesnt work :-(   It does nothing!! </p>
  
  <blockquote>
  <pre><code>string s = string.Format("{0}",strFilePath);
  
  NSUrl ns = NSUrl.FromFilename (s);   
  
  UIDocumentInteractionController PreviewController =
     UIDocumentInteractionController.FromUrl(ns);
  PreviewController.Delegate =  new UIDocumentInteractionControllerDelegateClass();
  PreviewController.PresentOpenInMenu(btnOpen,true);
  </code></pre>
  </blockquote>
  
  <hr>
  
  <pre><code>  public class UIDocumentInteractionControllerDelegateClass : UIDocumentInteractionControllerDelegate
                  {
                       public UIViewController FileViewController = new UIViewController();
                      public UIDocumentInteractionControllerDelegateClass ()
                      {
                      }
  
                      public override UIViewController ViewControllerForPreview (UIDocumentInteractionController controller)
                      {
                          return FileViewController;    
                      }
  
                      public override UIView ViewForPreview (UIDocumentInteractionController controller)
                      {
                          return FileViewController.View;
                      }
                  }
  </code></pre>