title: How to make a control from a StackPanel visible on top of another control
body: <p>In my window I have a <code>DockPanel</code> with a <code>StackPane</code>l holding a custom UserControl on the left, and a Grid with a ListBox on the right. My UserControl contains an <code>Expander</code> with a ListBox.</p>
  
  <p>This is the code from the window:</p>
  
  <pre class="lang-xml prettyprint-override"><code>&lt;Window ...&gt;
      &lt;DockPanel&gt;
          &lt;StackPanel Width="100" DockPanel.Dock="Left"&gt;
              &lt;localp:NeumesPanel/&gt; &lt;!-- This is the UserControl --&gt;
          &lt;/StackPanel&gt;
          &lt;Grid Margin="10" DockPanel.Dock="Right"&gt;
              &lt;ListBox .../&gt;
          &lt;/Grid&gt;
      &lt;/DockPanel&gt;
  &lt;/Window&gt;
  </code></pre>
  
  <p>Right now, when I expand the Expander, part of it doesn't show since the StackPanel's Width is narrower than the Width of Expander's content. Like this: <a href="http://screenshooter.net/100101493/xfcfxau" rel="nofollow">http://screenshooter.net/100101493/xfcfxau</a></p>
  
  <p>What I'd like to achieve is to have the Expander show over my Grid without compromising on the Grid's Width - I don't want the StackPanel wider than it currently is. How to do it? Is it possible?</p>