title: WPF Binding not updating with UpdateSourceTrigger=PropertyChanged
body: <p>I have a TabControl in which I set the DataContext to an instance of the <a href="http://pastebin.com/puKhVSs6" rel="nofollow" title="SettingsWrapper class">this</a> class, It's basicly a wrapper for DependencyProperties of a static class with the same properties. </p>
  
  <p>In my Markup I set the DataContext like this</p>
  
  <pre><code>&lt;TabControl DataContext="{Binding ElementName=self, Path=Settings}"&gt;
  </code></pre>
  
  <p>and binding to the property within the TabControl like this</p>
  
  <pre><code>&lt;TextBox Text="{Binding Path=Url, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" /&gt;
  </code></pre>
  
  <p>However, this does not lead to any updates of the source when the content of the TextBox is changed. I can change the content of the TextBox, let it loose focus etc. it does just not update the source. </p>