title: Accessing sub-namespaces of a XAML namespace without defining a new xmlns
body: <p>This might just be impossible by the nature of XAML but this is my situation:</p>
  
  <p>I am trying to access the namespace <code>NineGridViewer.ValidationRules</code> within my XAML. I currently have the namespace definition <code>xmlns:nineGridViewer="clr-namespace:NineGridViewer"</code>. Is it necessary to define a completely new namespace to access the ValidationRules namespace or is it possible to use my nineGridViewer xmlns to access subnamespaces?</p>