title: Binding Setting Property but UI not updating. Can I debug within referenced project/control?
body: <p>I have a custom control with bindings like below</p>
  
  <pre><code>&lt;DataTemplate DataType="{x:Type vm:EditorTabViewModel}"&gt;
      &lt;me:MarkdownEditor 
          Options="{Binding Path=Options, RelativeSource={RelativeSource AncestorType=Window}}" /&gt;
  &lt;/DataTemplate&gt;
  </code></pre>
  
  <p>I find that binding (<code>Window1.Options</code>) is being set (after stepping through code in debug mode), the markdown editor options (supposed to set Fonts, Colors etc) does not get set, or at least the UI does not update. I want to bug whats happening with in the <code>MarkdownEditor.xaml.cs</code> but thats another (referenced) project. How can I verify that the <code>MarkdownEditor.Options</code> is being set at least? </p>
  
  <p>I have actually tested that the <code>MarkdownEditor</code> side is working by the below</p>
  
  <pre><code>&lt;Window ...&gt;
      &lt;Grid&gt;
          &lt;Button Content="Options" Click="Button_Click" Grid.Row="0" /&gt;
          &lt;me:MarkdownEditor Options="{Binding Options, RelativeSource={RelativeSource AncestorType=Window}}" Grid.Row="1" /&gt;
      &lt;/Grid&gt;
  &lt;/Window&gt;
  </code></pre>
  
  <p>So the difference is the latter is a <code>MarkdownEditor</code> just in a <code>Grid</code> in a <code>Window</code>. The one failing is a <code>MarkdownEditor</code> within a <code>TabControl</code> bound to a <code>ObservableCollection&lt;TabViewModel&gt;</code></p>
  
  <p><strong>Visual Studio Solution Replicating The Problem</strong></p>
  
  <p>I am not really good at explaining things, so a simple project I made up minus all the unnecessary noise uploaded to <strong><a href="http://www.mediafire.com/?d88dsine5vug5gz" rel="nofollow noreferrer">media fire</a></strong> so you can take a look at whats wrong</p>
  
  <p>The video showing the problem on <strong><a href="http://screenr.com/hQc" rel="nofollow noreferrer">Screenr</a></strong></p>
  
  <p>With just a simple usage, editor in a window/grid. </p>
  
  <p><img src="https://imgur.com/8OjAG.jpg" alt=""></p>
  
  <p>the binding works ok</p>
  
  <p>Then when used in conjunction with <code>TabControl</code> bound to <code>ObservableCollection&lt;EditorTabViewModel&gt;</code>, the binding works as shown in the 2 <code>TextBox</code>es updating its values. but the editor does not update</p>
  
  <p><img src="https://imgur.com/p6Ub6.jpg" alt=""></p>