以JSON格式解析响应

{
   "response":{
      "code":200,
      "message":"OK",
      "data":[
         {
            "user":{
               "id":"564564",
               "firstName":"XYZ",
               "lastName":"J.",
               "photo":"https:'/'/img-s.example.com'/userpix_thumbs'/48935_12545435354.png",
               "gender":"male",
               "homeCity":"Algonquin, IL",
               "contact":{
               }
            },
            "lastCheckin":34634543532
         },
         {
            "user":{
               "id":"3254353",
               "firstName":"PQR",
               "lastName":"Black",
               "photo":"https:'/'/img-s.example.com'/userpix_thumbs'/TJZE1FSTWBE5JA11.jpg",
               "gender":"male",
               "homeCity":"Chicago, IL",
               "relationship":"friend",
               "contact":{
               }
            },
            "lastCheckin":3534523422345
         }
      ]
   }
}

以上为JSON的响应。我无法从上面的响应解析"用户"内容。它总是返回0而不是firstName和lastName字段。请帮助。下面是我的代码。

FSQAPIRec_CheckIn_Results g1 = new FSQAPIRec_CheckIn_Results();
HttpWebRequest req = (HttpWebRequest)WebRequest.Create(url);
HttpWebResponse resp = (HttpWebResponse)req.GetResponse();
StreamReader sr = new StreamReader(resp.GetResponseStream());
string json = sr.ReadToEnd();
sr.Close();
g1 = JSONHelper.Deserialise<FSQAPIRec_CheckIn_Results>(json);
if (g1.response.message == "OK")
{
    List<FSQCheckIn_Data> obj = g1.response.data;
    for (int i = 0; i < obj.Count(); i++)
        {
            List<FSQCheckIn_UserData> obj1 = obj[i].user;
            for (int j = 0; j < obj1.Count(); j++)
                lbl_Resent_Chechin.Text += (j + 1) + ") " + obj1[j].firstName + " " + obj1[j].lastName + "<br/><br/>";
        }
}

public class JSONHelper
{
    public static T Deserialise<T>(string json)
    {
        using (var ms = new MemoryStream(Encoding.Unicode.GetBytes(json)))
        {
            var serialiser = new DataContractJsonSerializer(typeof(T));
            return (T)serialiser.ReadObject(ms);
        }
    }
    public static string Serialize<T>(T obj)
    {
        DataContractJsonSerializer serializer = new      DataContractJsonSerializer(obj.GetType());
        using (MemoryStream ms = new MemoryStream())
        {
            serializer.WriteObject(ms, obj);
            return Encoding.Default.GetString(ms.ToArray());
        }
    }

[Serializable]
[DataContract]
public class FSQAPIRec_CheckIn_Results
{
    [DataMember]
    public RecCheckIn_Response response { get; set; }
}
[Serializable]
[DataContract]
public class RecCheckIn_Response
{
    [DataMember]
    public string code { get; set; }
    [DataMember]
    public string message { get; set; }
    [DataMember]
    public List<FSQCheckIn_Data> data { get; set; }
}
[Serializable]
[DataContract]
public class FSQCheckIn_Data
{
    [DataMember]
    public List<FSQCheckIn_UserData> user { get; set; }
}
[Serializable]
[DataContract]
public class FSQCheckIn_UserData
{
    [DataMember]
    public string firstName { get; set; }
    [DataMember]
    public string lastName { get; set; }
    [DataMember]
    public string photo { get; set; }
}