通过 XML HTTP 把文本文件载入 HTML 元素

新建一个.aspx文件

 <%@ Page Language="C#" AutoEventWireup="true" CodeFile="01-通过 XML HTTP 把文本文件载入 HTML 元素.aspx.cs"
     Inherits="_01_通过_XML_HTTP_把文本文件载入_HTML_元素" %>

 <!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 type="text/javascript">
         var xmlhttp;
         function loadXMLDoc(url)
         {
             xmlhttp = null;
             if (window.XMLHttpRequest)
             {
                 xmlhttp = new XMLHttpRequest();//所有现代浏览器（IE7+、Firefox、Chrome、Safari 以及 Opera）均内建 XMLHttpRequest 对象。
             }
             else
             {
                 xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");//老版本的 Internet Explorer （IE5 和 IE6）使用 ActiveX 对象
             }
             if (xmlhttp != null)
             {
                 xmlhttp.onreadystatechange = state_Change;
                 xmlhttp.open("GET", url, true);
                 xmlhttp.send(null);
             }
             else
             {
                 alert("Your browser does not support XMLHTTP.");
             }
         }

         function state_Change()
         {
             if (xmlhttp.readyState == 4)
             {// 4 = "loaded"
                 if (xmlhttp.status == 200)
                 {// 200 = "OK"
                     document.getElementById('T1').innerHTML = xmlhttp.responseText;
                 }
                 else
                 {
                     alert("Problem retrieving data:" + xmlhttp.statusText);
                 }
             }
         }
     </script>
 </head>
 <body onload="loadXMLDoc('test_xmlhttp.txt')">
     <div id="T1" style="border: 1px solid black; height: 40; width: 300; padding: 5">
     </div>
     <br />
     <button onclick="loadXMLDoc('test_xmlhttp2.txt')">
         Click</button>
 </body>
 </html>

test_xmlhttp.txt内容

This is a test using an XML HTTP request to show a text file.
If this text shows, it worked!

test_xmlhttp2.txt内容

This is another text file - shown WITHOUT re-loading the page! This is how the XML HTTP request object works!