title: Can't convert Resource to string using TypeConverter
body: <p>Exception:</p>
  
  <blockquote>
    <p>Cannot convert the value in attribute 'Text' to object of type
    'System.String'. Unable to cast object
    of type 'MyApp.Foo' to type
    'System.String'.</p>
  </blockquote>
  
  <p>XAML:</p>
  
  <pre><code>&lt;Window.Resources&gt;
    &lt;my:Foo x:Key="foo"&gt;&lt;/my:Foo&gt;
  &lt;/Window.Resources&gt;
  
  &lt;TextBox Text="{DynamicResource foo}"&gt;&lt;/TextBox&gt;
  </code></pre>
  
  <p>C#</p>
  
  <pre><code>[TypeConverter(typeof(FooConverter))]
  public class Foo
  {
      public Foo()
      {}
  }
  
  public class FooConverter : TypeConverter
  {
      public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)
      {
          return true;
      }
  
      public override object ConvertTo(ITypeDescriptorContext context, System.Globalization.CultureInfo culture, object value, Type destinationType)
      {
          return "Foo";
      }
  }
  </code></pre>
  
  <p>What is wrong?</p>