protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            SqlConnection conn = new SqlConnection();
            conn.ConnectionString = xxxx;
            conn.Open();
            SqlDataAdapter sda = new SqlDataAdapter("select s_kmbm,i_grade,s_bm1,s_bm2,s_bm3,s_bm4,s_bm5 from Table1 order by i_grade desc", conn);
            DataTable dt = new DataTable();
            try
            {
                sda.Fill(dt);
                sda.Dispose();
                conn.Close();
                conn.Dispose();
            }
            catch
            {
                sda.Dispose();
                conn.Close();
                conn.Dispose();
                conn = null;
                sda = null;
            }

            TreeNode tr = new TreeNode("根节点", "0");

            AddNode(tr, dt);
            this.TreeView1.Nodes.Clear();
            this.TreeView1.Nodes.Add(tr);
        }
    }
    private void AddNode(TreeNode tn, DataTable dt)
    {
        for (int i = 0; i < dt.Rows.Count; i++)
        {
            int grade = int.Parse(tn.Value) + 1;
            if (dt.Rows[i].ItemArray[1].ToString() == "1" && tn.Value == "0")
            {
                TreeNode subtn = new TreeNode(dt.Rows[i].ItemArray[0].ToString(), dt.Rows[i].ItemArray[1].ToString());
                AddNode(subtn, dt);
                tn.ChildNodes.Add(subtn);
            }
            else if ((int.Parse(dt.Rows[i].ItemArray[1].ToString()) - grade) == 0)
            {
                string pNode = "";
                for (int k = 2; k < grade + 1; k++)
                {
                    pNode += dt.Rows[i].ItemArray[k].ToString();
                }                if (pNode == tn.Text)
                {
                    TreeNode subtn = new TreeNode(dt.Rows[i].ItemArray[0].ToString(), dt.Rows[i].ItemArray[1].ToString());
                    AddNode(subtn, dt);
                    tn.ChildNodes.Add(subtn);
                }
            }
        }
    }