asp.net 2.0中TreeView（无限级）绑定数据库

数据库结构如图：

关键代码：

 1protected void Page_Load(object sender, EventArgs e)
 2    {
 3        if (!IsPostBack)
 4        {
 5            DataBindHelper.BindDropDown(this.DropDownList1, News_LocationDAL.Instance.GetList().Tables[0], "PK_Location", "LocationName");
 6            TreeNode rootnode = new TreeNode("新闻栏目", "0", "", "newscolright.aspx", "NewsColRight");
 7            rootnode.Expanded = true;
 8            TreeView1.Nodes.Add(rootnode);
 9            CreateTree("0", rootnode);
10        }
11    }
12    private void CreateTree(string belong, System.Web.UI.WebControls.TreeNode rootnode)
13    {
14        DataSet ds = News_ColumnDAL.Instance.GetListByPid(belong,this.DropDownList1.SelectedValue);
15
16        foreach (DataRow dr in ds.Tables[0].Rows)
17        {
18            TreeNode treenode = new TreeNode("", "", "", "newscolright.aspx", "NewsColRight");
19            treenode.Text = dr["NewsColName"].ToString().Trim();
20            treenode.Expanded = true;
21            rootnode.ChildNodes.Add(treenode);
22
23            string id = dr["PK_NewsCol"].ToString().Trim();
24            CreateTree(id, treenode);        
25            TreeNodeCollection childNodes = rootnode.ChildNodes;
26            childNodes[childNodes.Count - 1].NavigateUrl = "newscolright.aspx?NewsColID=" + dr["PK_NewsCol"].ToString() + "&NewsColPID=" + dr["NewsPID"] + "&PK_Location=" + dr["PK_Location"].ToString();
27        }
28    }