“没有 'IEnumerable<SelectListItem>' 类型的 ViewData 项具有键 'Skip'

Question

我正在尝试创建一个球员团队，每个团队有 4 名球员，所以我有 4 个 select 列表，其中包含并填充联盟中的球员。当我去救队时报错：

"There is no ViewData item of type 'IEnumerable' that has the key 'Skip'`

CreateTeam 控制器：

public ActionResult CreateLeagueTeam(int? id)
{
    int leagueId = id.Value;
    League league = db.Leagues.Include(x=>x.Members).First(l=> l.Id == leagueId);
    var leagueMemberList = league.Members.ToList();
    var leagueMemberSelectListItems = new List<SelectListItem>();
    foreach(Member m in leagueMemberList)
    {
        leagueMemberSelectListItems.Add(new SelectListItem() { Text = m.FirstName + " " + m.LastName, Value = m.Id.ToString() });
    }
    ViewData["leagueMemberList"] = leagueMemberSelectListItems;
    return View();  
}

HTTP POST ActionResult:

[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult CreateLeagueTeam([Bind(Include = "skip")] Team team)
{           
    team.IsBonspiel = false;
    team.IsLeague = true;
    // team.Name = team.Skip.LastName;
    team.YearActive = games.getSeasonYear();
    //finds and sets the league ID for the team
    int leagueId = (int)Session["leagueId"];
    League league = db.Leagues.Find(leagueId);
    team.League = league;
    if (ModelState.IsValid)
    {
        db.Teams.Add(team);
        db.SaveChanges();
        return RedirectToAction("Index");
    }
    return View(team);
}

最后是抛出错误的视图：

<div class="form-group">
    @Html.Label("Skip", null, htmlAttributes: new { @class = "control-label col-md-2" })
    <div class="col-md-10">
        @Html.DropDownListFor(model => model.Skip, (IEnumerable<SelectListItem>)ViewBag.leagueMemberList, htmlAttributes: new { @class = "control-label col-md-2" })
    </div>
</div>

还有团队模型：

public class Team: Entity
{
    [Required]
    public bool IsBonspiel { get; set; }
    [Required]
    public bool IsLeague { get; set; }
    [Required]
    public string Name { get; set; }
    [Required]
    public int YearActive { get; set; }
    public int? SkipId { get; set; }
    public Member Skip { get; set; }
    public string BonspielSkip { get; set; }
    public List<BonspielTeamMember> BonspielMembers { get; set; }
    public List<Member> Members { get; set; }
    public List<Game> Games { get; set; }
    public Bonspiel Bonspiel { get; set; }
    public League League { get; set; }
}

Answer 1

您向 "ViewData" 添加了数据，但您尝试从 ViewBag 访问。您应该知道 ViewData 与 ViewBag 不同。因此，您尝试更改此行：

 ViewData["leagueMemberList"] = leagueMemberSelectListItems;

至 => ViewBag.leagueMemberList = leagueMemberSelectListItems;

Answer 2

您的代码存在多个错误。

Skip 是一个复杂对象，您不能将 <select> 绑定到复杂的对象。根据你的看法，应该是 @Html.DropDownListFor(m => m.SkipId, ...)
您没有 ViewBag 属性名为 leagueMemberList （将控制器代码更改为 ViewBag.leagueMemberList = leagueMemberSelectListItems; 或将视图代码更改为 @Html.DropDownListFor(m => m.SkipId, (IEnumerable<SelectListItem>)ViewData["leagueMemberList"], ...)
您没有重新分配 ViewData["leagueMemberList"] 的值（或 ViewBag.leagueMemberList) 在 POST 方法中，如果 ModelState 是无效并且您 return 视图，这将导致不同的结果异常，因为它将是 null（参考 this question/answer
您在 POST 方法中的 [Bind(Include = "skip")] 代码意味着 ModelState 将始终无效，因为您排除了所有属性来自绑定的模型（除了 Skip 而你没有 post Skip)

“没有 'IEnumerable<SelectListItem>' 类型的 ViewData 项具有键 'Skip'

"There is no ViewData item of type 'IEnumerable<SelectListItem>' that has the key 'Skip'

c#

asp.net-mvc

selectlist