js ajax 传送xml dom对象到服务器

客户端代码
 1     <script>
        var isie = true;
        var xmlhttp = null;
        function createXMLHTTP() {//创建XMLXMLHttpRequest对象
            if (xmlhttp == null) {
                if (window.XMLHttpRequest) {
                    xmlhttp = new XMLHttpRequest();
                }
                else {
                    xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
                }
                //if (xmlhttp == null) {
                //    alert('你的浏览器不支持AJAX');
                //}
            }
        if ($.browser.msie) {//IE浏览器
                isie = true;
            }
            else {
                isie = false;
            }
            
        }
        //创建XML文档那个对象,也是第一步
        function createDomXml() {
            var domXml = null;
        //IE浏览器创建xml dom对象
            var signs = ["Msxml2.DOMDocument.5.0", "Msxml2.DOMDocument.4.0", 

"Msxml2.DOMDocument.3.0", "Msxml2.DOMDocument", "Microsoft.XmlDom"];
            for (var i = 0; i < signs.length; i++) {
                try {
                    domXml = new ActiveXObject(signs[i]);
                    break;
                }
                catch (e) { }
            }
        
            //其他浏览器
            if (domXml == null)
                domXml = document.implementation.createDocument("", "", null);
            return domXml;
        }
        //第二步：客户端获取数据写入xml文档对象里
        function createXml(dom) { 
            var root = doc.createElement("root");//创建根结点
            var assign_id = doc.createElement("id");//子节点
            var assign_ans = doc.createElement("answer");//子节点
            if (isie) {
                assign_id.text = "1";
                assign_ans.text = "1";
            }
            else {
                assign_id.textContent = "1";
                assign_ans.textContent = "1";
            }
            
            
            root.appendChild(assign_id);
            
            root.appendChild(assign_ans);
            
            dom.appendChild(choose);     
        }
        function submit() {
            var dom = createDomXml();
            createXMLHTTP();
            if (xmlhttp == null) {
                alert("你的浏览器不支持ajax,请换个浏览器试试");
                return 0;
            }
            createXml(dom);
            
            xmlhttp.onreadystatechange = success;
            xmlhttp.open("post", "test.aspx", true);//接收请求页面
            //xmlhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
            xmlhttp.send(dom);
        }

        function success()//异步处理函数，当服务成功返回时
        {
            if (xmlhttp.readyState == 4) {
                alert(xmlhttp.status);
                if (xmlhttp.status == 200) {
                    alert(xmlhttp.responseText);
                }
                else {
                    alert("test error");
                }
            }
        }
    </script>

服务器端代码 
1   protected void Page_Load(object sender, EventArgs e)
        {
        string res;
            Request.ContentEncoding = System.Text.Encoding.GetEncoding("UTF-8");
            XmlDocument xmlDoc = new XmlDocument();
            xmlDoc.Load(Request.InputStream);
            XmlNode node = xmlDoc.SelectSingleNode("choose");
            foreach (XmlNode child in node.ChildNodes)
            {
                res + child.innerText;
            }
        Response.Write(res);
        Response.End();
        }
    }