title: UserControl custom property grayed
body: <p>I'm quite sure this is a stupid question, but all my tries failed.<br>
  I have a custom control in which I'd like to have a complex property exposing many properties. I want to do this because I would have an <em>expandable</em> property in visual property manager, so I can set sub-properties easily because grouped together in parent property.
  This is a schema of what I've done:</p>
  
  <pre><code>public partial class QViewer : UserControl
  {
      private Shortcuts toolsShortcuts = new Shortcuts();
      private TestProp testProp = new TestProp();
  
      public Shortcuts ToolsShortcuts { get { return toolsShortcuts; } }
      public TestProp Test { get { return testProp; } }
  }
  
  
  public struct TestProp
  {
      public bool DoIt;
      public DateTime Date;
  }
  
  public class Shortcuts
  {
      Keys toolArrow = Keys.None;
      public Keys Arrow
      {
          get { return toolArrow; }
          set { ... }
      }
  }
  </code></pre>
  
  <p>}</p>
  
  <p>When I insert my custom control in a form (using another project inside same solution) and I open properties, both <em>Shortcuts</em> and <em>Test</em> are grayed, not expandable, so I can't set properties inside them.<br>
  What's wrong? Is there a better way to <strong>group</strong> properties than creating a class or a struct?<br>
  Thanks to everybody!</p>