title: The tag "xxx" does not exist in XML namespace"yyy" / Reference could not be found
body: <p>I have a winform usercontrol than I want to add to wpf project.</p>
  
  <p>I added the relevant references (WindowsFormsIntegration, SystemWindowsForms and my user control dll) and added this row in my XAML:</p>
  
  <pre><code>xmlns:MyControl="clr-namespace:xx.xx.xx;assembly=xx.xx"
  </code></pre>
  
  <p>And then this:</p>
  
  <pre><code>&lt;WindowsFormsHost&gt;&lt;MyControl:control&gt;&lt;/MyControl:control&gt;&lt;/WindowsFormsHost&gt;
  </code></pre>
  
  <p>When I write "MyControl:" the "control" is automated show up that mean VS recognize the control and all references added ok... but when I compile the project this give me the error in the title.</p>
  
  <p><strong>Edit</strong></p>
  
  <p>Its very strange when I'm compile the all project i've got error "The type or namespace name "xx' could not be found..."
  but I added all the refernces and the VS recognize the namespace so why the compiler don't found them? If this problem will be solved I beleive the other problem also will disappear.</p>