有一个内置虚拟类的“玩家”类，因为虚拟类而无法保存新玩家

Question

我有三节课。在我的创建视图中，我得到了一个加载所有FootballTeam的下拉列表。 但问题是当我发布到控制器时。因为ModelState.IsValid无效。我知道它与“公共虚拟FootballTeam FootballTeam {get; set;}”有关，因为它在我添加之前有效：）

我唯一想做的就是将玩家绑定到fotballs团队。我可以将我的“公共虚拟FootballTeam FootballTeam”更改为int而不是虚拟FootballTeam，这应该可行。 但我在这个Entity Framework one to many上看到，这是映射它的最佳方式，就像我使用虚拟FootballTeam一样。

        [HttpPost]
    public ActionResult CreatePlayer(PlayerViewModel playerViewModel)
    {
        var team = db.FootballTeam.Find(playerViewModel.Player.FootballTeam.Id);
        playerViewModel.Player.FootballTeam = team;

        if (ModelState.IsValid)
        {
            db.Player.Add(playerViewModel.Player);
            db.SaveChanges();
            return RedirectToAction("Teams");
        }
        return RedirectToAction("Teams");
    }


@model test.Models.PlayerViewModel

@Html.DropDownListFor(x => x.Player.FootballTeam.Id, Model.FootballTeams.Select(y => new SelectListItem
                                                                                        {
                                                                                            Text = y.Name,
                                                                                            Value = y.Id.ToString()
                                                                                        }))

    public class Player
{
    public int Id { get; set; }
    public int ImageId { get; set; }
    [Required(ErrorMessage = "Vänligen ange ett namn")]
    public string Name { get; set; }
    [Required(ErrorMessage = "Vänligen ange en possition")]
    public string Position { get; set; }
    [Required(ErrorMessage = "Vänligen ange födelseåret")]
    public string BirthYear { get; set; }
    [Required(ErrorMessage = "Vänligen ange en längd")]
    public string Length { get; set; }
    [Required(ErrorMessage = "Vänligen ange en vikt")]
    public string Weight { get; set; }
    [Required(ErrorMessage = "Vänligen ange moderklubben, alt ett '-'")]
    public string FirstClub { get; set; }
    public virtual FootballTeam FootballTeam { get; set; }
}

    public class FootballTeam
{
    public int Id { get; set; }
    [Required(ErrorMessage = "Vänligen ange ett namn")]
    public string Name { get; set; }
    public ICollection<Player> Players { get; set; }
    public ICollection<Coach> Coaches { get; set; }
    [Required(ErrorMessage = "Vänligen fyll i information om laget")]
    [DataType(DataType.MultilineText)]
    public string Information { get; set; }
}

    public class PlayerViewModel
{
    public Player Player { get; set; }
    public IEnumerable<Image> Image { get; set; }
    public IEnumerable<FootballTeam> FootballTeams { get; set; } 
}