C＃反序列化JSON Web API响应

我需要别人的帮助，他们可以告诉我我的错误在哪里。
我有一个返回JSON代码的API：

{"block4o": {
   "id": 20153910,
   "name": "Block4o",
   "profileIconId": 616,
   "revisionDate": 1408967362000,
   "summonerLevel": 30
}}

我试图对它进行反序列化，但是没有成功。我正在使用NuGet的NewtonSoft.Json。这是我的代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;
using System.Net;
using Newtonsoft.Json;

namespace ConsoleApplication37
{
    class Program
    {

        class MyData
        {
            public long id { get; set; }
            public string name { get; set; }
            public int profileIconId { get; set; }
            public long revisionDate { get; set; }
            public long summonerLevel { get; set; }
        }

        static void Main()
        {
            WebRequest request = WebRequest.Create(
              "https://eune.api.pvp.net/api/lol/eune/v1.4/summoner/by-name/Block4o?api_key=****");
            request.Credentials = CredentialCache.DefaultCredentials;
            WebResponse response = request.GetResponse();
            Stream dataStream = response.GetResponseStream();
            StreamReader reader = new StreamReader(dataStream);
            string responseFromServer = reader.ReadToEnd();
            Console.WriteLine(responseFromServer);
            reader.Close();
            response.Close();
            Console.ReadKey();

            MyData tmp = JsonConvert.DeserializeObject<MyData>(responseFromServer);
            Console.WriteLine("{0}",tmp.id);
            Console.ReadKey();
        }

    }
}

PS它的工作原理是：

{
   "id": 20153910,
   "name": "Block4o",
   "profileIconId": 616,
   "revisionDate": 1408967362000,
   "summonerLevel": 30
}