title: How to correctly handle keyboard in TreeView?
body: <p>I have a visual tree similar to the following one:</p>
  <pre><code>TreeView
      TreeViewItem
          ComboBox
      TreeViewItem
          TextBox
  </code></pre>
  <p>The visual tree is made from a few data templates, and a single <code>DataTemplateSelector</code>.</p>
  <p>The problem, when I press <kbd>↑</kbd> or <kbd>↓</kbd> on the keyboard when the element with the <code>ComboBox</code> has focus, <code>ComboBox</code> handles that key by switching the selected element.</p>
  <p>How to prevent <code>ComboBox</code> and <code>TextBox</code> controls inside the tree nodes from handling the keys which are used by <code>TreeView</code> keyboard navigation?</p>