html中代码：
<!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title></title> <script src="js/jquery-1.7.2.min.js"></script> </head> <body> <select id="sel1"> <option>加载中...</option> </select> <select id="sel2"> <option>加载中...</option> </select> <select id="sel3"> <option>加载中...</option> </select> <script type="text/javascript"> a($("#sel1"), "0001", "1"); $("#sel1").change(function () { a($("#sel2"), $("#sel1").val(), "2"); }); $("#sel2").change(function () { a($("#sel3"), $("#sel2").val(), "3"); }); function a(sel, code, count) { $.ajax({ url: "ashxs/china.ashx", data: { "code": code }, type: "post", dataType: "json", success: function (data) { sel.empty(); for (i in data) { sel.get(0).add(new Option(data[i].name, data[i].code)); } if (count == "1") { a($("#sel2"), $("#sel1").val(), "2"); } if (count == "2") { a($("#sel3"), $("#sel2").val(), "3"); } } });//ajax } </script> </body> </html>
一般处理程序中的代码：
<%@ WebHandler Language="C#" Class="china" %> using System; using System.Web; using System.Linq; using System.Data.Linq; using System.Collections; using System.Collections.Generic; public class china : IHttpHandler { DataClassesDataContext con = new DataClassesDataContext(); public void ProcessRequest(HttpContext context) { string end = "["; int count = 0; string code = context.Request["code"]; List<ChinaStates> list = con.ChinaStates.Where(r => r.ParentAreaCode == code).ToList(); if (list.Count > 0) { foreach (ChinaStates c in list) { if (count <= 0) { end += "{\"name\":\"" + c.AreaName + "\",\"code\":\"" + c.AreaCode + "\"}"; } else { end += ",{\"name\":\"" + c.AreaName + "\",\"code\":\"" + c.AreaCode + "\"}"; } count++; } } end += "]"; context.Response.Write(end); } public bool IsReusable { get { return false; } } }
原文：http://www.cnblogs.com/123lucy/p/5769713.html