啥叫异步,啥叫Ajax.咱不谈啥XMLHTTPRequest.通俗讲异步就是前台页面javascript能调用后台方法.这样就达到了无刷新.所谓的Ajax.这里我们讲二种方法方法一:(微软有自带Ajax框架)在里微软有自己的Ajax框架.就是在页面后台.cs文件里引入 using System.Web.Services 空间然后定义静态方法(方法前加上 [WebMethod])[WebMethod]public static string ABC(string ABC){return ABC;}好了,现在我们谈谈前台Js怎么处理后台返回的数据吧,可利用Jquery处理返回的纯html,json,Xml等数据.这里我们演示返回返回的数据有string、集合(List<>)、类.但都返回Json格式(Json轻量级比XML处理起来简单).看看前台是怎么解析这些数据的.代码如下:前台页面:<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default2.aspx.cs"Inherits="Default2" %><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN""/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="/1999/xhtml"><head runat="server"><title>无标题页</title><style type="text/css">.hover{cursor: pointer; /*小手*/background: #ffc; /*背景*/}</style><script type="text/javascript" src="js/jquery-1.3.2-vsdoc2.js"></script><script type="text/javascript">//无参数调用$(document).ready(function() {$('#btn1').click(function() {$.ajax({type: "POST", //访问WebService使用Post方式请求contentType: "application/json", //WebService 会返回Json类型url: "Default2.aspx/HelloWorld", //调用WebService的地址和方法名称组合 ---- WsURL/方法名data: "{}", //这里是要传递的参数，格式为 data: "{paraName:paraValue}",下面将会看到dataType: 'json',success: function(result) { //回调函数，result，返回值alert(result.d);}});});});//有参数调用$(document).ready(function() {$("#btn2").click(function() {$.ajax({type: "POST",contentType: "application/json",url: "Default2.aspx/GetWish",data: "{value1:'心想事成',value2:'万事如意',value3:'牛牛牛',value4:2009}", dataType: 'json',success: function(result) {alert(result.d);}});});});//返回集合（引用自网络，很说明问题）$(document).ready(function() {$("#btn3").click(function() {$.ajax({type: "POST",contentType: "application/json",url: "Default2.aspx/GetArray",data: "{i:10}",dataType: 'json',success: function(result) {$(result.d).each(function() {alert(this);$('#dictionary').append(this.toString() + " ");//alert(result.d.join(" | "));});}});});});//返回复合类型$(document).ready(function() {$('#btn4').click(function() {$.ajax({type: "POST",contentType: "application/json",url: "Default2.aspx/GetClass",data: "{}",dataType: 'json',success: function(result) {$(result.d).each(function() {//alert(this);$('#dictionary').append(this['ID'] + " " + this['Value']);//alert(result.d.join(" | "));});}});});});//Ajax 为用户提供反馈，他们两个方法可以添加给jQuery对象在Ajax前后回调//但对与Ajax的监控，本身是全局性的$(document).ready(function() {$('#loading').ajaxStart(function() {$(this).show();}).ajaxStop(function() {$(this).hide();});});// 鼠标移入移出效果，多个元素的时候，可以使用“，”隔开$(document).ready(function() {$('btn').hover(function() {$(this).addClass('hover');}, function() {$(this).removeClass('hover');});});</script></head><body><form id="form1" runat="server"><div><input type="button" id="btn1" value="HelloWorld"/><input type="button" id="btn2" value="传入参数"/><input type="button" id="btn3" value="返回集合"/><input type="button" id="btn4" value=" 返回复合类型"/></div><div id="dictionary">dictionary</div></form></body></html>后台.cs文件using System;using System.Collections;using System.Collections.Generic;using System.Configuration;using System.Data;using System.Linq;using System.Web;using System.Web.Security;using System.Web.UI;using System.Web.UI.HtmlControls;using System.Web.UI.WebControls;using System.Web.UI.WebControls.WebParts;using System.Web.Services;public partial class Default2 : System.Web.UI.Page{protected void Page_Load(object sender, EventArgs e){}[WebMethod]public static string HelloWorld(){return "123--->456";}[WebMethod]public static string ABC(string ABC){return ABC;}[WebMethod]public static string GetWish(string value1, string value2, string value3, int value4) {return string.Format("祝您在{3}年里 {0}、{1}、{2}", value1, value2, value3, value4); }/// <summary>/// 返回集合/// </summary>/// <param name="i"></param>/// <returns></returns>[WebMethod]public static List<int> GetArray(int i){List<int> list = new List<int>();while (i >= 0){list.Add(i--);}return list;}/// <summary>/// 返回一个复合类型/// </summary>/// <returns></returns>[WebMethod]public static Class1 GetClass(){return new Class1 { ID = "1", Value = "牛年大吉" };}public class Class1{public string ID { get; set; }public string Value { get; set; }}}利用Jquery让返回的各类数据(string、集合(List<>)、类)以Json数据格式返回,为什么要用到result.d 这里我们顺带讲下JsonJson简单讲就是Javascript对象或数组.Json形式一: javascript对象 { "firstName": "Brett", "lastName":"McLaughlin", "email": "aaaa" }Json形式二: javascript数组 [{ "firstName": "Brett", "lastName":"McLaughlin", "email": "aaaa" },{ "firstName": "Jason", "lastName":"Hunterwang", "email": "bbbb"}]当然javascript 数组和对象可以互相嵌套.如形式一中的"Brett"可以换成一个Js数组或Js对象.那微软的Ajax返回的是哪种形式呢.是第一种.微软框架默认返回一个 { "d": "后台返回的数据" } 这里我们用以上示例中的测试到得比如如上例的返回的是string类型的话Firefox调试如下当返回的是List<>类型的话FireFox调试如下返回的数据也是放在Js对象中的d属性里面所以说这就是为什么我们老是用result.d来取微软的框架返回的数据.方法一不常用.一般用得多的还是方法二.方法二:(建一个一般处理程序即.ashx文件)用这种方法一般是我们要在ashx文件里手动写好返回的Json格式的数据返回给前台用ashx 你可以配成Json格式一或Json格式二Default.aspx页面Js代码如下$.ajax({type: "POST",url: "Handler.ashx",dataType: "json",success: function(data){alert(); //返回的为 Json格式一(Js对象)/* 返回的为 Json格式二(Js对象)$(data).each(function(i) {alert(data[i].name);});*/}});Handler.ashx 代码如下<%@ WebHandler Language="C#" Class="Handler" %>using System;using System.Web;using System.Collections;using System.Collections.Generic;using System.Web.Script.Serialization;public class Handler : IHttpHandler {public void ProcessRequest (HttpContext context) {JavaScriptSerializer jss = new JavaScriptSerializer();context.Response.ContentType = "text/plain";// 返回的为Json格式一 Js对象string data = "{\"name\":\"wang\",\"age\":25}";// 返回的为Json格式二 Js数组//string data = "[{\"name\":\"wang\",\"age\":25},{\"name\":\"zhang\",\"age\":22}]"; context.Response.Write(data);}public bool IsReusable {get {return false;}}}以上基本上就第二种方法,可能有人不喜欢拼字符串.那有什么好办法呢?答案是有.微软对Json有很好的支持.拿上例子说我们只要把Handler.ashx改一下就可以了Handler.ashx 代码如下<%@ WebHandler Language="C#" Class="Handler" %>using System;using System.Web;using System.Collections;using System.Collections.Generic; // Dictionary<,> 键值对集合所需using System.Web.Script.Serialization; //JavaScriptSerializer 类所需public class Handler : IHttpHandler {public void ProcessRequest (HttpContext context) {JavaScriptSerializer jss = new JavaScriptSerializer();context.Response.ContentType = "text/plain";Dictionary<string, string> drow = new Dictionary<string, string>();drow.Add("name", "Wang");drow.Add("age", "24");context.Response.Write(jss.Serialize(drow));}public bool IsReusable {get {return false;}}}中的JavaScriptSerializer为我们提供了很好的方法jss.Serialize(drow) 是把drow的Dictionary<string, int> (键和值的集合)数据类型转换成Json数据格式调试结果如下图 (上面例子是输出了一个键值多集合即一个Json形式一的Js对象)如果要输出Json形式二(Js数组)呢? 我们也只要改动一部分就了Handler.ashx 代码如下<%@ WebHandler Language="C#" Class="Handler" %>using System;using System.Web;using System.Collections;using System.Collections.Generic;using System.Web.Script.Serialization;public class Handler : IHttpHandler {public void ProcessRequest (HttpContext context) {JavaScriptSerializer jss = new JavaScriptSerializer();context.Response.ContentType = "text/plain";List<Dictionary<string, string>> _list = new List<Dictionary<string, string>>();Dictionary<string, string> drow = new Dictionary<string, string>();drow.Add("name", "Wang");drow.Add("age", "24");Dictionary<string, string> drow1 = new Dictionary<string, string>();drow1.Add("name", "Zhang");drow1.Add("age", "35");_list.Add(drow);_list.Add(drow1);context.Response.Write(jss.Serialize(_list));}public bool IsReusable {get {return false;}}}调试结果如下图 (上面例子是输出了Json形式二的Js数组)讲到这里基本概念也讲得差不多了. 这里再讲一个够常碰到的例子就是如何把DataTabel转换成Json格式从而好让前台页面调用.就是在Handler.ashx写上一个方法/// <summary>/// DataTable转Json/// </summary>/// <param name="dtb"></param>/// <returns></returns>private string Dtb2Json(DataTable dtb){JavaScriptSerializer jss = new JavaScriptSerializer();ArrayList dic = new ArrayList();foreach (DataRow row in dtb.Rows){Dictionary<string, object> drow = new Dictionary<string, object>(); foreach (DataColumn col in dtb.Columns){drow.Add(col.ColumnName, row[col.ColumnName]);}dic.Add(drow);}return jss.Serialize(dic);}其实也有把Json格式转换成DataTabel格式,方法如下/// <summary>/// Json转DataTable/// </summary>/// <param name="json"></param>/// <returns></returns>private DataTable Json2Dtb(string json){JavaScriptSerializer jss = new JavaScriptSerializer();ArrayList dic = jss.Deserialize<ArrayList>(json);DataTable dtb = new DataTable();if (dic.Count > 0){foreach (Dictionary<string, object> drow in dic){if (dtb.Columns.Count == 0){foreach (string key in drow.Keys){dtb.Columns.Add(key, drow[key].GetType());}}DataRow row = dtb.NewRow();foreach (string key in drow.Keys){row[key] = drow[key];}dtb.Rows.Add(row);}}return dtb;}我们让返回的Json以表格的形式显示出来那么前台页面JS如下$.ajax({type: "POST",url: "Handler.ashx",dataType: "json",success: function(data){var table = $("<table border='1'></table>");for (var i = 0; i < data.length; i++) {o1 = data[i];var row = $("<tr></tr>");for (key in o1){var td = $("<td></td>");td.text(o1[key].toString());td.appendTo(row);}row.appendTo(table);}table.appendTo($("#back"));}});由上例子再讲两个Js知识点1. 之前我们取Json里面的数据如果是返回的是数组的话是用data[i].name也可表示为data[i]["name"]2. 如果要访问Js对象的说所有属性那么遍历Js对象.success: function(data){$(data).each(function(i) {for(key in this) // 遍历Js对象的所有属性alert(data[i][key]);//这里就不能换成 data[i].key 否则key成了属性而不是上面的key变量});}也有把前台Json数据传到后台后解析成DataTabel这里我把DataTabel软成Json和Json转成DataTabel写成一个例子.下载地址如下。