android--asp.net webservice 返回json

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Services;
using System.Web.Script.Services;
using System.Web.Script.Serialization;

[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
[System.Web.Script.Services.ScriptService]

public class Service : System.Web.Services.WebService
{
    public Service () {}

    [WebMethod]
    [ScriptMethod(ResponseFormat=ResponseFormat.Json)]
    public string Authenticate(string UserId, string UserPwd)
    {
        bool result = true;
        return new JavaScriptSerializer().Serialize(result);
    }

    [WebMethod]
    [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
    public string GetUser()
    {
        User user = new User();
        user.UserId = "jake";
        user.UserPwd = "";
        return new JavaScriptSerializer().Serialize(user);
    }

    [WebMethod]
    [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
    public string GetUsers()
    {
        List<User> list = new List<User>();
        User user = new User();
        user.UserId = "jake";
        user.UserPwd = "";
        list.Add(user);
        user.UserId = "nola";
        user.UserPwd = "";
        list.Add(user);
        return new JavaScriptSerializer().Serialize(list);
    }
}

public class User
{
    public string UserId { get; set; }
    public string UserPwd { get; set; }
}