ajaxwebmethodasp.net调用不成功需要什么设置吗

//test.aspx.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace Web
{
    public partial class test : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        [System.Web.Services.WebMethod]
        public static String GetString(string name)
        {
            return "Hello";
        }
    }
}

//test.aspx

    <script type="text/javascript">
        alert("1111111");
$.ajax({
            type: "POST",
            contentType: "application/json",
            url: "test.aspx/GetString",
            data: "{'name':'kevin'}",
            dataType: "json",
            success: function (theback) {
                //转换为json格式
                alert(theback.d)
//                var objd = eval('(' + theback.d + ')');
//                alert(objd.msg);
            },
            error:function(){alert("22222");}
        })
        </script>