title: extend a control
body: <p>In regular C#, if i want to extend my class, i inherit from the base one and add my class.
  I have a XAML UserControl, i want to add a new functionnality.
  For instance, i have a DataGrid, and i want to add a Contextmenu that allows to user to print.</p>
  
  <p>I don't quite see how should i inherit from the the usercontrol ?</p>
  
  <p>thanks
  Jon</p>