var s = "";
        $(function () {
            $("#open").click(function () {
                $.ajax({
                    type: "post",
                    url: "../Master/Ma.ashx",
                    data: { 'UserID': "admin" },
                    dataType: "json",
                    error: function () {
                        window.location.href = "/Web/Error.aspx";
                    },
                    success: function (json) {
                        alert(json);
                    }
                })


            })
        });    
这个是前台js




        public void ProcessRequest(HttpContext context)
        {
            context.Response.ContentType = "text/plain";
            string str = "";
            DataSet ds = new DataSet();
            string UserID = context.Request["UserID"].ToString();
            ds = DBhelper.ProcQueryData("Sp_GetNavigation", new IDataParameter[] { new SqlParameter("@UserID", UserID) });
            if (ds.Tables[0].Rows.Count > 0)
            {
                //将对象序列化为stringjson
                str = DataSetToJson(ds).ToString();
       
            }

            context.Response.Write(str);
        }



上面的是后台  。ashx

str



json的内容弹不出来！！！怎么回事啊？如果要访问json中的数据该如何写循环遍历？
苍天···