title: Where can you fined Application.Current.Dispatcher?
body: <p>This is very hard to find using Google. What Library is Application.Current.Dispatcher can be found? I cannot find it on my ClassLibrary project or cannot able to import its library.</p>
  
  <pre><code>Application.Current.Dispatcher.BeginInvoke(
      DispatcherPriority.Background,
      new Action(() =&gt; { 
         this.progressBar.Value = 50;
     }));
  </code></pre>