title: Adding property to TreeNode
body: <p>I have a webpage that uses a Treeview.
  In the treeview are nodes and i use the Text and Value property, but i need one more. I need one boolean property called IsFile.</p>
  
  <p>I make the Nodes and add them to the tree programmatically.
  I have a class Called NavTreeNodes that inherits the TreeNode class and ads this bool.</p>
  
  <pre><code>public class NavTreeNode : TreeNode
  {
      private bool _IsFile;
  
      public bool IsFile
      {
          get { return _IsFile; }
          set { _IsFile = value; }
      }
  
      public NavTreeNode()
      { }
  }
  </code></pre>
  
  <p>And when i make a new TreeNode i use this class.
  Everything works until i try to get the data from the treeview in the SelectedNodeChanged on the TreeView function.</p>
  
  <pre><code>protected void treeview_Navigation_SelectedNodeChanged(object sender, EventArgs e)
  {
      TreeNode node = treeview_Navigation.SelectedNode;
      NavTreeNode NNode = node as NavTreeNode;
  
      Response.Write(NNode.IsFile.ToString());
  }
  </code></pre>
  
  <p>I get a "Object reference not set to an instance of an object." error when i try this.
  I cant even get the Value or the Text value using this method.</p>