// 其它部分都一样

        //2.注册回调方法 callback
        xmlhttp.onreadystatechange = callback;

        //获取客户端内容
        var userName = document.getElementById("UserName").value;
        //进行编码解决 中文乱码
        userName = encodeURI(encodeURI(userName));

        // 进行跨域AJAX请求操作
        var url = "http://192.168.3.53/AjaxRequst.ashx";
        if (url.indexOf("http://") == 0) {
            //url = "http://192.168.3.53/AjaxRequst.ashx?name=123"
            //如果URL请求是上面类型,组合的URL将有两个?号,将?号转换成&
            url.replace("?", "&");
           
            //Proxy.ashx是同域的 代理服务程序,用于访问 跨域的 AJAX
            url = "Proxy.ashx?url=" + url;
        }    

        //Post 请求方式
        //3.设置和服务端交互的相应参数
        xmlhttp.open("Post", url, true);

        //Post方式需要增加的代码
        xmlhttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");

        //4.设置向服务器发送数据,启动和服务端的交互
        xmlhttp.send("name="+userName);

//这里用的是 Get 请求,Post传值麻烦
    
    public void ProcessRequest (HttpContext context) {
        context.Response.ContentType = "text/plain";
        
        string name = context.Request["name"].ToString();
        string url = context.Request["url"].ToString()+"?name="+name;
        
        string result = string.Empty;
        
        HttpWebRequest httpReq = (HttpWebRequest)WebRequest.Create(url);
        // 默认用 Get 请求,以下为Post请求但还未传值
        //httpReq.Method = "Post";
        //httpReq.ContentType = "application/x-www-form-urlencoded";
        
        HttpWebResponse HttpWResp = (HttpWebResponse)httpReq.GetResponse();
        System.IO.StreamReader reader = new System.IO.StreamReader(HttpWResp.GetResponseStream(), System.Text.Encoding.UTF8);
        result = reader.ReadToEnd();

        context.Response.Write(result);
        context.Response.End();  
    }

 public void ProcessRequest (HttpContext context) {
        context.Response.ContentType = "text/plain";
        if (context.Request["name"] == null)
        {
            context.Response.Write("用户名不能为空！");
            return;
        }
        
        string name = context.Request["name"].ToString();
        if (name != "xgao")
        {
            context.Response.Write(name+"用户可以注册！");
        }
        else
        {
            context.Response.Write(name + "用户以被注册！请更换用户名！");
        }
    }