Asp.net 2.0 Treeview 动态填充,并实现无限级树

Asp.net 2.0 Treeview 动态填充,并实现无限级树,
数据库表关键字段:
表: table1
 

type_id  type_name   per_type_id
   0        根目录               -1
   1        子目录                0
   2        子目录2             0
   3        子子目录              2
   .
   9        根目录二             -1

 C#代码

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;



public partial class tree : System.Web.UI.Page

效果: