title: XAML designer does not see C++/CX classes
body: <p>Windows Store project in C++/CX. I've placed an instance of the custom C++ class on a XAML page. I've marked it with a namespace. The project builds. Yet the design surface does not display the control, claims it's not present in the assembly. The XAML goes like this:</p>
  
  <pre><code>&lt;UserControl
  x:Class="MyApp.Foo"
  xmlns:local="using:MyApp"
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
  xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
  mc:Ignorable="d"
  d:DesignHeight="300"
  d:DesignWidth="400" Loaded="OnLoaded"&gt;
  
  ...
  &lt;local:MyControl x:Name="Bar" HorizontalAlignment="Left" VerticalAlignment="Top"/&gt;
  </code></pre>
  
  <p>The <code>MyControl</code> class is declared in code like this:</p>
  
  <pre><code>[Windows::Foundation::Metadata::WebHostHidden]
  public ref class MyControl sealed : Windows::UI::Xaml::Controls::Canvas
  {
   ...
  };
  </code></pre>
  
  <p>It has a public default contructor with no parameters. What's wrong here, please?</p>