title: treeView with checkBoxes for selected nodes
body: <p>I'm working with application, which use TreeView. I want some nodes have 
  checkBoxes, but not all.
  I know that I can do:</p>
  
  <pre><code>    treeView.CheckBoxes = true;
  </code></pre>
  
  <p>But then all nodes have checkBox. How can I add checkBox only for selected
  nodes?</p>