C# MVC ViewModel 返回 Null - 回传

Question

在我看来，我有很多奖项，每个奖项中都有相应的资格列表。我创建了一个 ViewModel 来显示每个奖项，单击一个按钮就会出现一个模态及其相关资格，用户可以将其标记为已完成/更新。但是，在发布数据时，它没有绑定(bind)到我的 Controller 方法中的 ViewModel。数据在我看来如预期般出现，每个奖项仅显示其相关资格。我已使用 FormCollection 访问某些字段以进行测试，并且正在回发数据。任何帮助都会很棒!

View 模型

public class CandidateExtended
{
    public CandidateExtended()
    {
        this.Qualifications = new List<Qualification_Extended>();
    }

    public int AwardID { get; set; }
    public int FrameworkID { get; set; }
    public string ULN { get; set; }
    public string Forename { get; set; }
    public string Surname { get; set; }
    public string TitleShort { get; set; }
    public string TitleFull { get; set; }
    public DateTime DOB { get; set; }
    public string Award { get; set; }
    public int AwardLevel { get; set; }
    public string Status { get; set; }
    public string Completion { get; set; }
    public string SelectedRoute { get; set; }

    public List<Qualification_Extended> Qualifications { get; set; }

    public void addQualification(Qualification_Extended qualification)
    {
        Qualifications.Add(qualification);
    }
}

Controller

  [HttpGet]
    public ActionResult Index()
    {

        var awardDetails = (from award in db.award
                            join candidate in db.candidate
                            on award.ULN equals candidate.ULN
                            join framework in db.framework
                            on award.QAN equals framework.QAN
                            where award.OrganisationIdentityID == organisationID
                            select new AwardDetails_Extended
                            {
                                AwardID = award.AwardID,
                                ULN = award.ULN,
                                AwardStatus = award.AwardStatus,
                                Forename = candidate.Forename,
                                Surname = candidate.Surname,
                                DOB = candidate.DOB,
                                FrameworkID = framework.FrameworkID,
                                TitleFull = framework.TitleFull,
                                TitleShort = framework.TitleShort, 
                                AwardLevel = framework.AwardLevel, 
                                Award = framework.Award,
                                Completion = framework.Completion
                            }).ToList();


        var qualificationDetails = (from candidateQualification in db.candidateQualification
                                    join qualification in db.qualification
                                    on candidateQualification.QualificationID equals qualification.QualificationID
                                    select new Qualification_Extended
                                    {
                                        ID = candidateQualification.ID,
                                        QualificationID = candidateQualification.QualificationID,
                                        ULN = candidateQualification.ULN,
                                        FrameworkID = candidateQualification.FrameworkID,
                                        Achieved = candidateQualification.Achieved,
                                        DateAchieved = candidateQualification.DateAchieved
                                    }).ToList();


        List<CandidateExtended> candidateVM = new List<CandidateExtended>();

        foreach (var item in awardDetails)
        {
            CandidateExtended vm = new CandidateExtended();
            vm.AwardID = item.AwardID;
            vm.FrameworkID = item.FrameworkID;
            vm.ULN = item.ULN;
            vm.Forename = item.Forename;
            vm.Surname = item.Surname;
            vm.DOB = item.DOB;
            vm.TitleShort = item.TitleShort;
            vm.TitleFull = item.TitleFull;
            vm.Award = item.Award;
            vm.AwardLevel = item.AwardLevel;
            vm.Status = item.AwardStatus;
            vm.Completion = item.Completion;
            vm.SelectedRoute = item.SelectedRoute;

            foreach (var qualification in qualificationDetails)
            {
                if (qualification.ULN == item.ULN && qualification.FrameworkID == item.FrameworkID)
                {
                    vm.addQualification(qualification);
                }
            }

            candidateVM.Add(vm);
        }

        return View(candidateVM);      
    }

查看

@using (Html.BeginForm("UpdateAward", "Organisation", FormMethod.Post))
{
@Html.HiddenFor(a => award.AwardID) 

<div class="row">
        <div class="col-md-12">
        <div class="row org-row-main">
            <div class="col-md-7"><h4 class="org-type">Qualification</h4></div>
            <div class="col-md-2"><h5 class="org-completed">Completed</h5></div>
            <div class="col-md-3"><h5 class="org-date">Date</h5></div>
        </div>

        <hr class="org-hr"/>

            @for (int i = 0; i < award.Qualifications.Count(); i++)
            {

                var qualification = award.Qualifications[i];

            <div class="row org-row">
                <div class="col-md-7">
                    @Html.HiddenFor(a => award.Qualifications[i].ID)
                </div>
                <div class="col-md-2">
                        @Html.CheckBoxFor(a => award.Qualifications[i].Achieved)
                </div>
                <div class="col-md-3">@Html.TextBoxFor(a => award.Qualifications[i].DateAchieved, "{0:dd/MM/yyyy}")
                </div>
            </div>
            }
        </div>
</div> 

<button type="submit" class="btn admin-button" style="margin-top: 0;">Save</button>

}

更新奖

[HttpPost]
    public ActionResult UpdateAward(CandidateExtended model, FormCollection collection)
    {

        return RedirectToAction("Index", "Login");

    }

Answer 1

首先(你可能已经有了这个，但我们看不到):你的 View 应该以包含 @model List<CandidateExtended> 的行开始(在内部 Type 前加上适当的命名空间)。

然后在 View 中你应该使用Model ，这是在 @model 之后指定的确切类型的定义关键字。

我们看到您正在使用 award ，我们看不到它来自哪里，大概是使用类似 var award = Model[j] 的东西设置的或 foreach (var award in Model) .
永远不要在 View 中使用此类临时变量或辅助变量(为了提高效率)来呈现表单； View 需要所有对象的完全限定名称，例如Model.Item[x].SubItem[y] 以生成可用于模型绑定(bind)的表单字段名称。

例如这:@Html.HiddenFor(a => award.Qualifications[i].ID)
应该是:@Html.HiddenFor(a => Model[j].Qualifications[i].ID)

并在所有其他地方进行相同的更改。

然后按照已经建议的那样做，使用List<...>在你的 Controller Post 方法中。

最后还请删除FormCollection ，如果您按照此处所述设置了所有内容，则不需要。体面的 MVC 代码从不使用FormCollection , 曾经。