问在接受表单后，没有类型为“IEnumerable<SelectListItem>”的IEnumerable<SelectListItem>项具有密钥。

EN

public class Player 
{
    public int Id { get; set; }
    [MinLength(1)]
    public string Name { get; set; }
    [MinLength(4)]
    public string LastName { get; set; }
    [DataType(DataType.Date)]
    public DateTime Birthdate { get; set; }

    public virtual Club Club { get; set; }     
}

public class Club 
{
    public int Id { get; set; }
    [StringLength(30, MinimumLength = 3)]
    [Required]
    public string Name { get; set; }
    [DataType(DataType.Date)]
    public DateTime Founded { get; set; }
    public virtual ICollection<Player> Players { get; set; }

    public override string ToString() {
        return Name;
    }
}

 // GET: /Players/Create
    public ActionResult Create() {
        //SelectList selectList = new SelectList(db.Clubs, "Id", "Name");
        ViewBag.Clubs = new SelectList(db.Clubs, "Id", "Name");
        return View();
    }

    // POST: /Players/Create
    // To protect from overposting attacks, please enable the specific properties you want to bind to, for 
    // more details see http://go.microsoft.com/fwlink/?LinkId=317598.
    [HttpPost]
    [ValidateAntiForgeryToken]
    public ActionResult Create([Bind(Include = "Id,Name,LastName,Birthdate,Club")] Player player) {
        if (ModelState.IsValid) {
            db.Players.Add(player);
            db.SaveChanges();
            return RedirectToAction("Index");
        }

        return View(player);
    }

<div class="form-group">
        @Html.LabelFor(model => model.Club, htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
      @Html.DropDownListFor(player => player.Club, (SelectList)ViewBag.Clubs)
            @Html.ValidationMessageFor(model => model.Club)
        </div>
    </div>