根据特殊的表数据，生成树

根据特殊的表数据，生成树

用的是最笨的方法，哪位有好的方法可以指教一下

protected void btGetTreeview_Click(object sender, EventArgs e)
    {
        TreeView1.Nodes.Clear();
        TreeView1.Visible = true;
        DataSet ds = pkhead.readData("select * from [group] where group_code='00'");
        if (ds.Tables.Count == 0) return;
        foreach (DataRow dr in ds.Tables[0].Rows)
        {
            TreeNode treenode = new TreeNode();
            treenode.Text = pubfunc.ObjectToString(dr["group_name"]);
            treenode.Value = pubfunc.ObjectToString(dr["group_code"]);
            TreeView1.Nodes.Add(treenode);
            string sql2 = string.Format("select * from [group] where group_code like '{0}%' and len=2 order by group_code", treenode.Value);
            DataSet ds2 = pkhead.readData(sql2);
            if (ds2.Tables.Count == 0) return;
            foreach (DataRow dr2 in ds2.Tables[0].Rows)
            {
                TreeNode treenode2 = new TreeNode();
                treenode2.Text = pubfunc.ObjectToString(dr2["group_name"]);
                treenode2.Value = pubfunc.ObjectToString(dr2["group_code"]);
                treenode.ChildNodes.Add(treenode2);
                string sql3 = string.Format("select * from [group] where group_code like '{0}%' and len=3 order by group_code", treenode2.Value);
                DataSet ds3 = pkhead.readData(sql3);
                if (ds3.Tables.Count == 0) return;
                foreach (DataRow dr3 in ds3.Tables[0].Rows)
                {
                    TreeNode treenode3 = new TreeNode();
                    treenode3.Text = pubfunc.ObjectToString(dr3["group_name"]);
                    treenode3.Value = pubfunc.ObjectToString(dr3["group_code"]);
                    treenode2.ChildNodes.Add(treenode3);
                    string sql4 = string.Format("select * from [group] where group_code like '{0}%' and len=4 order by group_code", treenode3.Value);
                    DataSet ds4 = pkhead.readData(sql4);
                    if (ds4.Tables.Count == 0) return;
                    foreach (DataRow dr4 in ds4.Tables[0].Rows)
                    {
                        TreeNode treenode4 = new TreeNode();
                        treenode4.Text = pubfunc.ObjectToString(dr4["group_name"]);
                        treenode4.Value = pubfunc.ObjectToString(dr4["group_code"]);
                        treenode3.ChildNodes.Add(treenode4);
                        string sql5 = string.Format("select * from [group] where group_code like '{0}%' and len=5 order by group_code", treenode4.Value);
                        DataSet ds5 = pkhead.readData(sql5);
                        if (ds4.Tables.Count == 0) return;
                        foreach (DataRow dr5 in ds5.Tables[0].Rows)
                        {
                            TreeNode treenode5 = new TreeNode();
                            treenode5.Text = pubfunc.ObjectToString(dr5["group_name"]);
                            treenode5.Value = pubfunc.ObjectToString(dr5["group_code"]);
                            treenode4.ChildNodes.Add(treenode5);
                        }

                    }
                }
            }
        }
    }