asp.net Treeview控件

        string ConnString = @"Data Source=.;Initial Catalog=master;Integrated Security=true;";
        private DataTable dt = null;
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                dt = new DataTable();

                GetMenuToDataTable("select * from treeview", dt);

                BindTree(dt, null, "0");
            }

        }
        private void BindTree(DataTable dtSource, TreeNode parentNode, string parentID)
        {

            DataRow[] rows = dtSource.Select(string.Format("f_ParentNodeId={0}", parentID));

            foreach (DataRow row in rows)
            {

                TreeNode node = new TreeNode();

                node.Text = row["f_Name"].ToString();

                node.Value = row["f_NodeId"].ToString();
                node.NavigateUrl = row["f_Url"].ToString();
                BindTree(dtSource, node, row["f_NodeId"].ToString());

                if (parentNode == null)
                {

                    TreeView1.Nodes.Add(node);

                }

                else
                {

                    parentNode.ChildNodes.Add(node);

                }

            }

        }
        private DataTable GetMenuToDataTable(string query, DataTable dt)
        {

            using (SqlConnection conn = new SqlConnection(ConnString))
            {

                SqlCommand cmd = new SqlCommand(query, conn);

                SqlDataAdapter ada = new SqlDataAdapter(cmd);

                ada.Fill(dt);

            }

            return dt;

        }

CREATE TABLE treeview
 (
    f_i_autoid INT IDENTITY(1,1),
    f_NodeId INT,
    f_ParentNodeId INT,
    f_Name VARCHAR(20),
    f_Tag VARCHAR(20),
    f_Url NVARCHAR(400),
    f_order INT ,
    f_isHidden TEXT,
    f_datetime DATETIME
 )
INSERT INTO treeview VALUES(1,0,'互联网站','互联网站','#',0,'asdf',GETDATE())
INSERT INTO treeview VALUES(2,1,'百度','互联网站','http://baidu.com',0,'baidu',GETDATE())
INSERT INTO treeview VALUES(3,1,'新浪','互联网站','http://www.sina.com.cn',0,'sina',GETDATE())
INSERT INTO treeview VALUES(4,1,'腾讯','互联网站','http://www.tencent.com',0,'tencent',GETDATE())
INSERT INTO treeview VALUES(5,1,'搜狐','互联网站','http://www.sohu.com',0,'sohu',GETDATE())