asp.net jquery ajax数据操作 DropDownList级联

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1、定义一个类 CityCounty.cs文件，如下：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Runtime.Serialization;/// <summary>
///CityCounty 的摘要说明
/// </summary>
[DataContract]
public class CityCounty
{[DataMember]private int menu_ID;public int Menu_ID{get { return menu_ID; }set { menu_ID = value; }}[DataMember]private string menu_Name;public string Menu_Name{get { return menu_Name; }set { menu_Name = value; }}
}

2、定义一个Json处理类，ToJson.cs文件，如下：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Runtime.Serialization.Json;
using System.IO;/// <summary>
///JsonHelper 的摘要说明
/// </summary>
public static class JsonHelper
{//转换为Json格式输出public static string ToJson(this object obj){DataContractJsonSerializer serializer = new DataContractJsonSerializer(obj.GetType());Stream stream = new MemoryStream();serializer.WriteObject(stream, obj);stream.Position = 0;StreamReader streamReader = new StreamReader(stream);return streamReader.ReadToEnd();}
}

3、定义Default4.aspx及Default4.aspx.cs文件，如下：

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default4.aspx.cs" Inherits="Default4" %><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server"><title></title><script src="jquery.js" type="text/javascript"></script><script type="text/javascript" language="javascript">$(function () {$("#DropDownList1").change(function () {$.ajax({url: "Default5.aspx?id=" + $(this).val(),data: null,dataType: "json",success: function (data) {$("#DropDownList2").empty();//第一种方法//for (var i = 0; i < data.length; i++) {//$("<option value='" + data[i]["menu_ID"] + "'>" + data[i]["menu_Name"] + "</option>").appendTo("#DropDownList2");//}//第二种方法  用下面的方法也能够循环输出 .each方法$.each(data, function (i) {$("<option value='" + data[i]["menu_ID"] + "'>" + data[i]["menu_Name"] + "</option>").appendTo("#DropDownList2");})}});});});</script>
</head>
<body><form id="form1" runat="server"><div><div><asp:Label ID="lblone" runat="server" Text="市" /><asp:DropDownList ID="DropDownList1" runat="server"></asp:DropDownList><asp:Label ID="lbltwo" runat="server" Text="县" /><asp:DropDownList ID="DropDownList2" runat="server"><asp:ListItem Text="--请选择市--" Value="1"></asp:ListItem></asp:DropDownList></div></div></form>
</body>
</html>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using USTC;
using System.Data;public partial class Default4 : System.Web.UI.Page
{DM dm = new DM();protected void Page_Load(object sender, EventArgs e){if (!IsPostBack){string strSQL = "select * from UDS_Menu where Menu_ID like '%____00%'";DataSet ds = dm.getsql(strSQL);this.DropDownList1.DataSource = ds;this.DropDownList1.DataTextField = "Menu_Name";this.DropDownList1.DataValueField = "Menu_ID";this.DropDownList1.DataBind();this.DropDownList1.Items.Insert(0,"--请选择城市--");}}
}

4、定义Default5.aspx及Default5.aspx.cs文件，如下：

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default5.aspx.cs" Inherits="TEST_Default5" %><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server"><title></title>
</head>
<body><form id="form1" runat="server"><div></div></form>
</body>
</html>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using USTC;
using System.Data;public partial class TEST_Default5 : System.Web.UI.Page
{DM dm = new DM();protected void Page_Load(object sender, EventArgs e){if (!IsPostBack){IList<CityCounty> list = new List<CityCounty>();string id = Request.QueryString["id"].ToString();string strSQL = "select Menu_ID,Menu_Name from UDS_Menu where Super_Menu_ID=" + int.Parse(id);DataSet ds = dm.getsql(strSQL);for (int i = 0; i < ds.Tables[0].Rows.Count; i++){CityCounty c = new CityCounty();c.Menu_ID = Convert.ToInt32(ds.Tables[0].Rows[i]["Menu_ID"].ToString());c.Menu_Name = ds.Tables[0].Rows[i]["Menu_Name"].ToString();list.Add(c);}Response.Write(list.ToJson());Response.End();}}
}