如何使用asp.net TreeView递归循环子节点生成树形菜单？

/// <summary>
/// 生成根节点
/// </summary>
/// <param name="treeview"></param>
protected void BindTreeView(long ID, TreeView treeview)
{
  DataTable dt = menuLogic.GetMenu2(ID, User.Identity.Name);
  treeview.Nodes.Clear();
  DataRow[] parentrow = dt.Select("par_id=0");
  for (int i = 0; i < parentrow.Length; i++)
  {
   TreeNode rootnode = new TreeNode();
   rootnode.Text = parentrow[i]["node_name"].ToString(); //parentrow[i][3].ToString();
   rootnode.Value = parentrow[i]["ID"].ToString(); //parentrow[i][1].ToString(); 主键
   rootnode.Expanded = true;
   rootnode.Selected = false;
   rootnode.SelectAction = TreeNodeSelectAction.None;
   treeview.Nodes.Add(rootnode);
   CreateChildNode(rootnode, dt); //
  }
}
/// <summary>
/// 生成子节点
/// </summary>
/// <param name="parentNode"></param>
/// <param name="datatable"></param>
protected void CreateChildNode(TreeNode parentNode, DataTable datatable)
{
  DataRow[] rowlist = datatable.Select("par_id=" + parentNode.Value);
  for (int i = 0; i < rowlist.Length; i++)
  {
   TreeNode node = new TreeNode();
   if (datatable.Select("par_id=" + rowlist[i]["ID"].ToString().Trim()).Length > 0)
   {
    node.Text = rowlist[i]["node_name"].ToString();
    node.Value = rowlist[i]["ID"].ToString();
   }
   else
   {
    node.Text = "<a href=\"javascript:;\" onclick=\"OpenUrl('" + rowlist[i]["url"].ToString().Trim() + "',this)\">" + rowlist[i]["node_name"].ToString() + "</a>";
    node.Value = rowlist[i]["ID"].ToString();
   }
   node.Expanded = false;
   node.Selected = false;
   node.SelectAction = TreeNodeSelectAction.None;
   parentNode.ChildNodes.Add(node);
   CreateChildNode(node, datatable); //递归调用
  }
}