title: WPF Custom Control - ItemsControl template not being applied
body: <p>I'm building a custom WPF control that derives from TabControl.  In the ControlTemplate, I'm using a ItemsControl to display a list that is being bound from the template (an observable collection of type FileMenuItem).  During program execution, I'm getting the following error in the output window:</p>
  
  <blockquote>
    <p>ItemTemplate and ItemTemplateSelector
    are ignored for items already of the
    ItemsControl's container type;
    Type='FileMenuItem'</p>
  </blockquote>
  
  <p>The type FileMenuItem is derived from MenuItem.  If I change the base class to DependencyObject, the code actually runs and the template is applied (so that's an option).  I googled the error and couldn't find anything about it, has anyone run into this while developing custom controls?  Even though I have a workaround, I'd like to understand what's happening, and I think using the MenuItem as a base class is a cleaner implementation.</p>
  
  <p>I can post more code if it would help.  Thanks!</p>