title: DockPanel is not visible even though it is set to visible
body: <p>I have a <code>DockPanel</code> inside another <code>DockPanel</code> the first one is set to be docked on the whole form, but the second one is set on the top of the form and it has three buttons inside it, the background color of it is set to grey, and I can see the content blue border in the editor but it doesn't have a color or a text in it, and when I run the application there is nothing no button no colors nothing.</p>
  <p>Here is the XAML code:</p>
  <pre><code>&lt;Grid Background=&quot;White&quot;&gt;
      &lt;DockPanel Name=&quot;MainBackground&quot;&gt;
          &lt;DockPanel Name=&quot;Top&quot; Height=&quot;32&quot; Background=&quot;#FF707070&quot; DockPanel.Dock=&quot;Top&quot; Margin=&quot;0, 0, 0, 1000&quot;&gt;
  
              &lt;Button
              Width=&quot;46&quot;
              Height=&quot;32&quot;
              DockPanel.Dock=&quot;Right&quot;
              Margin=&quot;687,0,0,398&quot;
              Background=&quot;White&quot; Click=&quot;Button_Click_1&quot;&gt;
  
                  &lt;StackPanel Orientation=&quot;Horizontal&quot;&gt;
                      &lt;Image Source=&quot;Res/RDI.png&quot; Width=&quot;20&quot; Height=&quot;20&quot;/&gt;
                  &lt;/StackPanel&gt;
  
              &lt;/Button&gt;
              &lt;Button
              Width=&quot;46&quot;
              Height=&quot;32&quot;
              Content=&quot;×&quot; 
              FontSize=&quot;20&quot; DockPanel.Dock=&quot;Right&quot; Click=&quot;Button_Click&quot; Margin=&quot;734,0,0,398&quot; Background=&quot;White&quot;/&gt;
  
          &lt;/DockPanel&gt;
      &lt;/DockPanel&gt;
  &lt;/Grid&gt;
  </code></pre>