三级联动

新建ChinaStates类

 1 using System;
 2 using System.Collections.Generic;
 3 using System.Linq;
 4 using System.Web;
 5 
 6 /// <summary>
 7 /// ChinaStatesDA 的摘要说明
 8 /// </summary>
 9 public class ChinaStatesDA
10 {
11     private DataClassesDataContext Context;
12     public ChinaStatesDA()
13     {
14         //
15         // TODO: 在此处添加构造函数逻辑
16         //
17         Context = new DataClassesDataContext();
18     }
19     public List<ChinaStates> select(string parentcode)
20     {
21         return Context.ChinaStates.Where(r=>r.ParentAreaCode==parentcode).ToList();
22     }
23 }

后端代码

 1 using System;
 2 using System.Collections.Generic;
 3 using System.Linq;
 4 using System.Web;
 5 using System.Web.UI;
 6 using System.Web.UI.WebControls;
 7 
 8 public partial class Default2 : System.Web.UI.Page
 9 {
10     protected void Page_Load(object sender, EventArgs e)
11     {
12         if (!IsPostBack)
13         {
14             binddl(DropDownList1,"0001");
15         }
16     }
17     private void binddl(DropDownList ddl, string code)
18     {
19         ddl.Items.Clear();
20         ddl.Items.Add("--请选择--");
21         foreach (ChinaStates data in new ChinaStatesDA().select(code))
22         {
23             ListItem it = new ListItem(data.AreaName, data.AreaCode);
24             ddl.Items.Add(it);
25         }
26       }
27     protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
28     {
29         binddl(DropDownList2, DropDownList1.SelectedValue); ;
30     }
31     protected void DropDownList2_SelectedIndexChanged(object sender, EventArgs e)
32     {
33         binddl(DropDownList3,DropDownList2.SelectedValue);
34     }
35 }