title: Expand all nodes in a TreeView
body: <p>I have a treeview bound to collection of objects using MVVM. However, i need to expand all the nodes of the treeview by default.
  Tried using style:</p>
  
  <pre><code>&lt;Style TargetType="TreeViewItem"&gt;
   &lt;Setter Property="IsExpanded" Value="True"/&gt;
  &lt;/Style&gt;
  </code></pre>
  
  <p>But that does not work.. </p>