title: Get TreeViewItem datacontext from root container
body: <p>I have a Window with two use controls. One encapsulates a TreeView control and another is marely a string representation of a selected TreeViewItems details.</p>
  
  <p>TreeView controls is already self sufficient - it will populate itself with content items. Each TreeViewItem has a datacontext.</p>
  
  <p>Here is what I need to happen:</p>
  
  <ol>
  <li>Whenever a user clicks an item, it generates a Selected routed event that is being caught at the root container of my window.</li>
  <li>I need the event handler, that handles Selected routed event to be able to get some data (a property value) from the selected TreeViewItem's data context.</li>
  <li>Based on this value, my event handler will create a DetailsView control and will populate it with data.</li>
  </ol>
  
  <p>Is my approach correct, in respect to handling the Selected events? How can I get the property value from my selected items data context? </p>
  
  <p>Thank you.</p>