asp.net webapi

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Http;
using WebApplication1.Models;

namespace WebApplication1.Controllers
{
    [RoutePrefix("api/Test")]
    public class TestController : ApiController
    {
        // GET: Test
        [Route("Index")]
        [HttpPost]
        public UserInfo Index(UserInfo userInfo)
        {
            return userInfo;
        }
    }
}

<div class="jumbotron">
    <h1>ASP.NET</h1>
    <script src="~/Scripts/jquery-1.10.2.js"></script>
    <script type="text/javascript">
        var userInfo = {"UserName":"chm","Age":3};
        $(function () {
            $("#btnTest").click(function () {
                $.ajax({
                    type: "POST",
                    url: "/api/Test/Index",
                    data:userInfo,
                    success: function (data) {
                        alert(data.UserName+data.Age);
                    }
                });
            });
        });
    </script>
</div>
<div >
    <input type="button" id="btnTest" value="test"/>
</div>