最近正在拜读<<Ajax in Action>>这本书，运用书中知识，结合.net，写了这篇用.net 处理xmlHttp发送异步请求的文章。
我们要达到的目的是点击按钮，获得服务器的当前时间，aspx的html如下：
Html
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="Linkedu.Web.WebWWW.Default" %>
<!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>测试</title>
<script language="javascript" src="javascript/prototype/extras-array.js"></script>
<script language="javascript" src="javascript/xmlHttp.js"></script>
<script language="javascript" src="javascript/eventRouter.js"></script>
<script language="javascript" src="Default.js"></script>
<script language="javascript">
</script>
</head>
<body>
<form id="form1" runat="server">
用Post方式获得服务器的当前时间
<input id="btnTestPost" type="button" value="Post" />
用Get方式获得服务器的当前时间
<input id="btnTestGet" type="button" value="Get" />
<div id="divResult"></div>
</form>
</body>
</html>
要用javascript 发送xmlHttp 请求必须解决的问题是跨浏览器的支持。我们把xmlHttp的发送封装在一个javascript对象中，同时在这个对象中解决了跨浏览器支持的问题。代码如下：
xmlHttp对象
/**//*
url-loading object and a request queue built on top of it
*/
/**//* namespacing object */
var net=new Object();
net.READY_STATE_UNINITIALIZED=0;
net.READY_STATE_LOADING=1;
net.READY_STATE_LOADED=2;
net.READY_STATE_INTERACTIVE=3;
net.READY_STATE_COMPLETE=4;
/**//*--- content loader object for cross-browser requests ---*/
net.xmlHttp=function(url, onload, params, method, contentType, onerror){
this.req=null;
this.onload=onload;
this.onerror=(onerror) ? onerror : this.defaultError;
if(typeof(method) == "undefined" || method == null)
{
method = "POST";
}
this.loadXMLDoc(url, params, method, contentType);
}
net.xmlHttp.prototype.loadXMLDoc=function(url, params, method, contentType){
if (!method){
method="GET";
}
if (!contentType && method=="POST"){
contentType='application/x-www-form-urlencoded';
}
if (window.XmlHttpRequest){
this.req=new XmlHttpRequest();
} else if (window.ActiveXObject){
this.req=new ActiveXObject("Microsoft.xmlHttp");
}
if (this.req){
try{
var loader=this;
this.req.onreadystatechange=function(){
net.xmlHttp.onReadyState.call(loader);
}
this.req.open(method,url,true);
if (contentType){
this.req.setRequestHeader('Content-Type', contentType);
}
this.req.send(params);
}catch (err){
this.onerror.call(this);
}
}
}
