title: The given key was not present in the dictionary - error and warnings
body: <p>I'm making an app in WPF and blend and all of a sudden I get those errors and can't see the app design</p>
  
  <p><img src="https://i.stack.imgur.com/a5XpU.png" alt="example screenshot"></p>
  
  <p>when I press on the error its takes me to the XAML and show me that 'Window' is not good</p>
  
  <p>On the other side, I can run the app with no problems</p>
  
  <p>thanks for any help!</p>