title: WPF TreeView drag and drop using preview
body: <p>I'm handling drag and drop events in a TreeView using PreviewMouseDown, PreviewMouseMove and PreviewMouseUp, however, there is an issue.</p>
  
  <p>In my PreviewMouseDown handler, I set everything ready in case there's a drag started (detected in the Move event), however I set e.Handled = true. This means that standard selection events don't get generated on my tree!</p>
  
  <p>What I want to be able to do in my Up event is to invoke the standard treeview selection changed event - except I cannot call events outside of the tree. So what's the correct way to do this?</p>
  
  <p>I have tried using the standard MouseDown, MouseMove and MouseUp events however there's an issue with messing up my multiple selection feature that means I need to use the Preview version of those events.</p>