the method JsonConvert.DeserializeObject converts id's into zero

I've got a string:

string model = "{\"Game\":{\"GameId\":1,\"Board\":[0,0,0,0,0,0,0,0,0],\"User1Id\":1,\"User2Id\":2,\"UserIdTurn\":1,\"WinnerId\":0,\"IsGameOver\":false},\"User\":{\"UserId\":1,\"UserName\":\"a\",\"Password\":\"a\",\"Password2\":\"a\",\"Games\":[]}}" 

And when I use this code:

GameModel myModel = JsonConvert.DeserializeObject<GameModel>(model);

It works pretty good but with only one problem - it changes my Game and User id's into zero. why does it happen and how can I solve it? I write in c# by the way.

those are my classes :

        public class GameModel
    {

        public Game Game { get; set; }

        public User User { get; set; }

    }

public class Game
    {

        public Game()
        {
            Board = new SquareState[9];                     
        }

        public Game(int user1Id)
        {
            Board = new SquareState[9];
            User1Id = user1Id;
            UserIdTurn = user1Id;
        }
        public int GameId { get; private set; }

        public SquareState[] Board { get; set; }

        [Required]
        public int User1Id { get; set; }

        public int User2Id { get; set; }

        public int UserIdTurn { get; set; }


        public int WinnerId { get; set; }

        public bool IsGameOver { get; set; }

    }

    public class User
    {
        public User()
        {
            Games = new List<Game>();
        }
        public int UserId { get; private set; }

        [Required]
        [Display(Name = "User Name:")]
        public string UserName { get; set; }


        [Required]
        [DataType(DataType.Password)]
        public string Password { get; set; }

        [Required]
        [Display(Name = "re-enter Password")]
        [DataType(DataType.Password)]
        [Compare("Password", ErrorMessage = "Passwords not match")]
        public string Password2 { get; set; }

        public List<Game> Games { get; set; }
    }