How to display TreeView as the dropdown of the ComboBox in XPMenus in the WinForms XPToolBar?

private TreeNode FindNode(TreeNodeCollection nodes, string text)
{
   foreach (TreeNode child in nodes)
      if (child.Text == text)
         return child;
   foreach (TreeNode child in nodes)
   {
      TreeNode matched = this.FindNode(child.Nodes, text);
      if (matched != null)
         return matched;
   }
return null;
}
private void comboDropDown1_DropDown(object sender, EventArgs e)
{
   // Before the drop-down is shown, select a TreeNode based on the text in the combo.
   if (this.comboDropDown1.Text != String.Empty)
   {
      TreeNode matchedNode = this.FindNode(this.treeView1.Nodes, this.comboDropDown1.Text);
      this.treeView1.SelectedNode = matchedNode;
   }
}

Private Function FindNode(ByVal nodes As TreeNodeCollection, ByVal text As String) As TreeNode
   For Each child As TreeNode In nodes
       If child.Text = text Then
          Return child
       End If
   Next child
   For Each child As TreeNode In nodes
       Dim matched As TreeNode = Me.FindNode(child.Nodes, text)
       If matched IsNot Nothing Then
          Return matched
       End If
   Next child
   Return Nothing
End Function
Private Sub comboDropDown1_DropDown(ByVal sender As Object, ByVal e As EventArgs) Handles comboDropDown1.DropDown
   '' Before the drop-down is shown, select a TreeNode based on the text in the combo.
   If Me.comboDropDown1.Text <> String.Empty Then
      Dim matchedNode As TreeNode = Me.FindNode(Me.treeView1.Nodes, Me.comboDropDown1.Text)
      Me.treeView1.SelectedNode = matchedNode
   End If
End Sub