title: Not visible content of WindowsFormsHost when added to WrapPanel in WPF application
body: <p>EDIT: To introduce quickly: <code>WindowsFormsHost</code> added by <code>xaml</code> has all contents. Added by <code>C#</code> has no contents---> pictures below.</p>
  
  <p>When I insert a <code>WindowsFormsHost</code> in the <code>WrapPanel x:Name = "VideoPanel"</code> by the <code>XAML</code> and then add <code>VideoStream videoStream</code> in the <strong>.cs</strong> file, conents of VideoStream are visible in the that <code>WrapPanel</code>. Everything is OK contents are visible(screenshot below).</p>
  
  <p>Adnotation: <code>VideoStream</code> extends <code>System.Windows.Forms.UserControl</code></p>
  
  <p><strong>XAML:</strong></p>
  
  <pre><code>   &lt;WrapPanel x:Name="VideoPanel" &gt;
                 &lt;Border BorderBrush="Green" BorderThickness="2"&gt;
                          &lt;WindowsFormsHost x:Name="Host" Width="400" Height="400"&gt;&lt;/WindowsFormsHost&gt;
                      &lt;/Border&gt;
     &lt;/WrapPanel&gt;
  </code></pre>
  
  <p><strong>.cs File:</strong></p>
  
  <pre><code>VideoStream videoStream = new VideoStream();
  Host.Child = VideoStream;
  </code></pre>
  
  <p><strong>Result</strong>(correct result): </p>
  
  <p><img src="https://i.stack.imgur.com/9iNIG.png" alt="enter image description here"></p>
  
  <hr>
  
  <p><strong>But</strong> when I want to create and insert <code>WindowsFormsHost</code> and the <code>VideoStream</code> in the <code>WrapPanel</code> by  C# code there is only border visible with no contents. <strong>How to make contents of <code>VideoStream</code> visible?</strong></p>
  
  <p><strong>Code with which I have problem:</strong></p>
  
  <pre><code>   WindowsFormsHost formsHost = new WindowsFormsHost();
          VideoStream videoStream = new VideoStream();
          formsHost.Child = videoStream;
          Border lineBorder = new Border();
          lineBorder.BorderBrush = Brushes.Green;
          lineBorder.BorderThickness = new Thickness(2);
          lineBorder.Child = new WindowsFormsHost();
          VideoPanel.Children.Add(lineBorder);
          videoStream.Height = 400;
          videoStream.Width = 400;
          lineBorder.Width = 400;
          lineBorder.Height = 400;
          formsHost.Width = 400;
          formsHost.Height = 400;
  </code></pre>
  
  <p><strong>XAML:</strong></p>
  
  <pre><code>  &lt;WrapPanel x:Name="VideoPanel" &gt;
              &lt;/WrapPanel&gt;
  </code></pre>
  
  <p><strong>Result</strong>(incorrect):</p>
  
  <p><img src="https://i.stack.imgur.com/5HYhJ.png" alt="enter image description here"></p>
  
  <p><strong>How to make contents of <code>VideoStream</code> visible?</strong></p>