title: ContentControl does not show change
body: <p>The following code is in a MEF MVVM desktop application.
  The Shell is already build, but a Module is initialising.
  The Module wants to add text to a ContentControl in the Shell, but the following code does not cause the change to be seen in the Shell Window.
  Any suggestions as to how I get the window to update.</p>
  
  <p>thanks</p>
  
  <pre><code>    [ImportingConstructor]
      public ModuleInit(IView1Model vm)
      {
          var viewModel = vm as ViewModels.View1Model;
          var view1 = GetView(viewModel);
  
          var shellModel = viewModel.Shell;
          var shellView = GetView(shellModel);
  
          Control c1 = shellview as Control; //Window
          ContentControl c2 = c1.FindName("ActiveItem1") as ContentControl;
          TextBlock tb = new TextBlock();
          tb.Text = "New Text Message";
          c2.Content = tb;
  </code></pre>
  
  <p>John</p>