title: Wpf usercontrol base, cannot create an instance
body: <p>I add an Usercontrol base class</p>
  
  <p>my Base Class</p>
  
  <pre><code> public class UserControlBase : UserControl
      {
          protected IAppLogic app;
          public  MainWindow CurrentWindow{
              get{
                  return (App.Current.MainWindow as MainWindow);
              }
          }
  
  
  
          public UserControlBase()
          {
              var _app = IoC.Kernel.Get&lt;IAppLogic&gt;();
              this.app = _app;
          }
  
          public void MainNavigate(Pages.PageBase p)
          {
              CurrentWindow.MainFrame.Content = p;
          }
      }
  </code></pre>
  
  <p>but the design does not shown</p>
  
  <p><a href="https://i.stack.imgur.com/5ysKx.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/5ysKx.png" alt="enter image description here"></a></p>