title: asp.net TreeView -keep the same state after postback
body: <p>I have a TreeView</p>
  
  <pre><code>&lt;asp:TreeView ID="tvCategories"   runat="server" ShowLines="false"  ShowExpandCollapse="true"  ExpandDepth="0"   /&gt;
  </code></pre>
  
  <p>by default the list is not expended. It has a plus symbol (+) to expand the sub nodes.</p>
  
  <p>when i expand the sub node and click on the sub node to show the content. once it shows the content the TreeView goes back to default state (collapses).</p>
  
  <p>How do I make it stay as it was before clicking on the sub node.... expended? (keep the same state after postback)? Thanks</p>