动态MVC RadioButton组选择的答案

Question

我有一个动态填充的问题和答案列表。

两个问题：

1. 回发后不显示问题和答案
2. 所选答案丢失

视图模型

public class RegistrationViewModel : RegisterExternalLoginModel
{
    //...etc...
    public Question Question { get; set; }
    public Answer Answer { get; set; }
    public List<Question> Questions { get; set; }
    public IList<Answer> PossibleAnswers { get; set; }
    public List<SelectedAnswer> SelectedAnswers { get; set; }
    public IList<SelectedAnswer> PreviousAnswers 
    { 
        set 
        { 
            foreach(Question q in Questions)
            {
                q.SelectedAnswers = value.Where(t => t.questionId == q.objectId).ToList() ;
            }
        } 
    }
}

选择答案

 public Answer SelectedAnswer 
    { 
        get 
        {
            if (SelectedAnswers != null && SelectedAnswers.Count > 0)
            {
                var answers = SelectedAnswers.Where(t => t.questionId == objectId);
                if (answers.Count() == 1) 
                {
                    var result = Answers.Where(t => t.objectId == answers.First().answerId).First();
                    return result;
                }
            }
            return null;
        } 
    }

的ActionResult

 public ActionResult CreateQuestions()
    {
        RegistrationViewModel vm = new RegistrationViewModel();
        IQFacade facade = new QFacade(CreateUserContext(true));

        //Questions and Answers
        vm.Questions = facade.GetQuestions().ToList();
        vm.PossibleAnswers = facade.GetPossibleAnswers();

        return View(vm);

    }

岗位

 [HttpPost]
 public ActionResult CreateQuestions(RegistrationViewModel vm)
    {
        var context = CreateUserContext(true);

            try{
                IQFacade f = new QFacade(context);
                f.CreateSomething(vm.User.name, vm.etc, vm.SelectedAnswers);//Need all the answers here, but null
            }
            catch (Exception ex)
            {
                //error stuff, etc...
                return View(vm);//the questions do not appear after this point. Do I need to bind them again from GetQuestions or shouldn't they still be a part of the vm object that I am returning?
            }
        }

        return RedirectToAction("Index");
    }

在视图中，我正在使用编辑器模板

 @Html.EditorFor(x => x.Questions)

模板

  @foreach (var possibleAnswer in Model.Answers)
{
    <div class="radio">
        @Html.RadioButtonFor(question => question.SelectedAnswer, possibleAnswer.objectId, new { id = possibleAnswer.objectId })

        <label for="@possibleAnswer.objectId">@possibleAnswer.text <span>@possibleAnswer.value</span></label> <p>@possibleAnswer.description</p>
    </div>
}

一切都在第一次生效，但在回发之后却无效。 我已经阅读了数十篇类似的SO帖子。 我想念什么？

Answer 1

根据评论，您的模型应该类似（不确定所有模型属性，因此我在这里做一些假设）

public class QuestionVM
{
  public int ID { get; set; } // for binding
  public string Text { get; set; }
  [Required]
  public int? SelectedAnswer { get; set; } // for binding
  public IEnumerable<Answer> PossibleAnswers { get; set; }
}

public class RegistrationViewModel : RegisterExternalLoginModel
{
  public RegistrationViewModel()
  {
    Questions = new List<QuestionVM>();
  }
  //...etc...
  public List<QuestionVM> Questions { get; set; }
}

GET方法

public ActionResult CreateQuestions()
{
    RegistrationViewModel vm = new RegistrationViewModel();
    .....
    // Populate the questions and answers
    var questions = facade.GetQuestions().ToList();
    var answers = facade.GetPossibleAnswers();
    foreach (var question in questions)
    {
      QuestionVM qvm = new QuestionVM();
      qvm.ID = question.ID;
      qvm.Test = question.Text;
      // Add possible answers for the question
      qvm.PossibleAnswers = answers.Where(a => a.QuestionID ==  question.ID);
      // If loading existing questions/answers for existing user, also set value of current SelectedAnswer so its selected by default in the view
      vm.Questions.Add(qvm);
    }
    return View(vm);
}

视图

@model YourAssembly.RegistrationViewModel
....

@for(int i = 0; i < Model.Questions.Count; i++)
{
  @Html.HiddenFor(m > m.Questions[i].ID) // for binding
  @Html.DisplayFor(m > m.Questions[i].Text)
  foreach(var answer in Model.Questions[i].PossibleAnswers)
  {
    @Html.RadioButtonFor(m => m.Questions[i].SelectedAnswer, answer.ID, new { id = answer.ID})
    <label for="@answer.ID">answer.Text</label>
  }
}

POST方法

[HttpPost]
public ActionResult CreateQuestions(RegistrationViewModel vm)
{
  if (!ModelState.IsValid)
  {
    // You need to rebuild the question text and possible answers because these are not posted back
    return View(vm);
  }
  // Your model is now populated with the ID of each question and the selected answer which can be saved to the database

请注意，您可以为问题和答案文本值添加隐藏的输入，以便它们回发，但是通常，它可以更好地重新加载到控制器中（如果您包括正确的数据注释并包括客户端验证，则该模型应始终在回发时有效）无论如何）