title: Unity activation error occured while trying to get instance of type
body: <p>I am using Prism 4 with Unity Extensions and the MVVM pattern. </p>
  
  <pre><code>public class Bootstrapper : UnityBootstrapper {
      protected override void InitializeShell() {
          Application.Current.RootVisual = (UIElement) Shell;
      }
  
      protected override DependencyObject CreateShell()
      {
          return ServiceLocator.Current.GetInstance&lt;Shell&gt;();
      }
  }
  </code></pre>
  
  <p>ServiceLocator.Current.GetInstance() throws the following exception :</p>
  
  <blockquote>
    <p>Activation error occured while trying to get instance of type Shell,
    key ""</p>
  </blockquote>