treeview 选中节点

        /// <summary>
        /// 绑定tMenu节点    一级节点
        /// </summary>
        private void bindTreeView()
        {
            StringBuilder sqlWebDisc = new StringBuilder();
            sqlWebDisc.AppendFormat("select * from tMenu where iLevel={0} order by dOrder asc", "1"); //1是根节点
            DataTable dt = new DataTable();
            dt = dbHelper.selectDatas(sqlWebDisc.ToString());            trvMenu.Nodes.Clear();//清空结点            foreach (DataRow dr in dt.Rows)
            {
                if (getLimit(dr["cLimit"].ToString()))//权限判断，如果有权限
                {
                    TreeNode node = new TreeNode();
                    node.SelectAction = TreeNodeSelectAction.Expand; //单击‘展开’或‘收缩’节点（不选中）
                    node.Text = dr["cMenuName"].ToString();
                    node.Value = dr["iMenuID"].ToString();
                    node.Expanded = true;                    trvMenu.Nodes.Add(node);
                    AddReplies(node, node.Value);
                }
            }
        }//绑定子节点
  private void AddReplies(TreeNode node, string nodevalue)
        {
            StringBuilder sqlWebDisc = new StringBuilder();
            sqlWebDisc.AppendFormat("select * from tMenu where iParnetMenuID={0} order by dOrder asc", nodevalue);
            DataTable dt = new DataTable();
            dt = dbHelper.selectDatas(sqlWebDisc.ToString());            foreach (DataRow dr in dt.Rows)
            {
                if (getLimit(dr["cLimit"].ToString()))//权限判断，如果有权限
                {                    TreeNode replyNode = new TreeNode();                    if (dr["iLevel"].ToString() == "2") //2是父节点
                    {
                        replyNode.SelectAction = TreeNodeSelectAction.Expand; //单击‘展开’或‘收缩’节点（不选中）
                    }
                    if (dr["iLevel"].ToString() == "3") //3是子节点
                    {
                        replyNode.SelectAction = TreeNodeSelectAction.Select; //单击‘展开’或‘收缩’节点（不选中）
                    }                    if (dr["cLink"].ToString() != String.Empty)
                    {
                        //  replyNode.NavigateUrl = dr["cLink"].ToString();
                        //  replyNode.Target = "mainFrame";                    }                    replyNode.Value = dr["iMenuID"].ToString();
                    replyNode.Text = dr["cMenuName"].ToString();
                    replyNode.Expanded = false;
                    node.ChildNodes.Add(replyNode);
                    AddReplies(replyNode, replyNode.Value);
                }
            }
        }
选择第三极节点的时候，想把url链接地址赋给一个label，让它显示url，但是总选不中节点，调试的时候label中有值，执行完后就为空了。