ASP.NET MVC 5 组单选按钮

Question

我正在开始我的第一个 ASP.NET MVC 项目，所以我有一个简单的问题。我有以下代码：

foreach(var question in Model.GeneralQuestions)
{
    <div class = "well">
        <h3>
            <strong>@question.QuestionString</strong>
        </h3>
        @foreach (var answer in question.PossibleAnswers)
        {
            @Html.RadioButtonFor(model => question.QuestionString, answer.Answer)
            @Html.Label(answer.Answer)
            <br />
        }
    </div>
}

Model.GeneralQuestions中的所有问题都是唯一的，因此单选按钮应按名称属性分组（每个问题一组单选按钮）。但是这段代码只产生一组，所以当我回答第二个问题时，第一个被取消选择。我需要改变什么？

编辑
我的模型看起来像：

public class StudentViewModel
{
    public Student Student { get; set; }
    public List<Question> GeneralQuestions { get; set; }
    public List<SubjectQuestions> SubjectQuestions { get; set; }
}
public class Student
{
    public int StudentID { get; set; }
    public string Index { get; set; }
    public string Name { get; set; }
    public string Surname { get; set; }

    public virtual ICollection<Subject> Subjects { get; set; }
}
public class Question
{
    public int QuestionID { get; set; }
    public string QuestionString { get; set; }
    public bool IsAssociatedWithSubject { get; set; }

    public virtual ICollection<PossibleAnswer> PossibleAnswers { get; set; }
    public virtual ICollection<Results> Results { get; set; }
}
public class SubjectQuestions
{
    public Subject Subject { get; set; }
    public List<Question> Questions { get; set; }
}
public class Results
{
    public int ResultsID { get; set; }
    public int QuestionID { get; set; }
    public int? SubjectID { get; set; }
    public int PossibleAnswerID { get; set; }

    public virtual Question Question { get; set; }
    public virtual PossibleAnswer PossibleAnswer { get; set; }
    public virtual Subject Subject { get; set; }
}

在 StudentViewModel 的一个实例中，我保存了一名学生和他应该回答的所有问题（包括一般问题和与他正在学习的科目相关的问题）并将其传递给查看。在视图中，我将所有问题都放在单一形式中，它们都是无线电类型。那么，任何人都可以帮助我对单选按钮进行分组并正确回发此表单吗？

Answer 1

您的代码存在许多问题，包括生成重复的 id（无效的 html），生成重复的 name 属性（这就是为什么您只创建一组，但更重要的是，这将阻止您在 post 返回时绑定到模型）并且您实际上并没有绑定到有效的属性。

您将需要创建视图模型来表示您想要显示和编辑的内容，并在 for 循环（或使用 EditorTemplate）中生成单选按钮，以便它们正确命名为索引器。

查看型号

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<AnswerVM> PossibleAnswers { get; set; }
}

public class SubjectVM
{
  public int? ID { get; set; }
  [DisplayFormat(NullDisplayText = "General")]
  public string Name { get; set; }
  public List<QuestionVM> Questions { get; set; }
}

public class AnswerVM
{
  public int ID { get; set; }
  public string Text { get; set; }
}

public class StudentVM
{
  public int ID { get; set; }
  public string Name { get; set; }
  // plus any other properties of student that you want to display in the view
  public List<SubjectVM> Subjects { get; set; }
}

查看

@model YourAssembly.StudentVM
@using(Html.BeginForm())
{
  @Html.HiddenFor(m => m.ID)
  @Html.DisplayFor(m => m.Name)
  for(int i = 0; i < Model.Subjects.Count; i++)
  {
    @Html.HiddenFor(m => m.Subjects[i].ID)
    @Html.DisplayFor(m => m.Subjects[i].Name) // will display "General" if no name
    for (int j = 0; j < Model.Subjects[i].Questions.Count; j++)
    {
      @Html.HiddenFor(m => m.Subjects[i].Questions[j].ID)
      @Html.DisplayFor(m => m.Subjects[i].Questions[j].Text)
      foreach(var answer in Model.Subjects[i].Questions[j].PossibleAnswers )
      {
        <div>
          @Html.RadioButtonFor(m => m.Subjects[i].Questions[j].SelectedAnswer, answer.ID, new { id = answer.ID})
          <label for="@answer.ID">@answer.Text</label>
        </div>
      }
      @Html.ValidationMessageFor(m => m.Subjects[i].Questions[j].SelectedAnswer)
    }
  }
  <input type="submit" value="save" />
}

控制器

public ActionResult Edit(int ID)
{
  StudentVM model = new StudentVM();
  // populate your view model with values from the database
  return View(model);
}

[HttpPost]
public ActionResult Edit(StudentVM model)
{
  // save and redirect
}

请注意，您的模型隐含的数据库结构让我有些困惑（例如，为什么 Question 和 SubjectQuestion 需要单独的模型，而 null 的值是 SubjectID 将其标识为 "General" 问题）。我建议您首先在 GET 方法中硬编码一些值，看看它是如何工作的，然后 posts 回来。

StudentVM model = new StudentVM();
model.ID = 1;
model.Name = "bambiinela";
model.Subjects = new List<SubjectVM>()
{
  new SubjectVM()
  {
    Questions = new List<QuestionVM>()
    {
      new QuestionVM()
      {
        ID = 1,
        Text = "Question 1",
        SelectedAnswer = ?, // set this if you want to preselect an option
        PossibleAnswers = new List<AnswerVM>()
        {
          new AnswerVM()
          {
            ID = 1,
            Text = "Answer A"
          },
          new AnswerVM()
          {
            ID = 1,
            Text = "Answer B"
          }
        }
      },
      new QuestionVM()
      {
        ID = 2,
        Text = "Question 2",
        PossibleAnswers = new List<AnswerVM>()
        {
          // similar to above
        }
      }
    }
  },
  new SubjectVM()
  {
    ID = 1,
    Name = "Math",
    Questions = new List<QuestionVM>()
    {
      // similar to above
    }
  }
};

当您 post 时，模型会填充每个主题中每个问题的所选答案的 ID。请注意 DisplayFor() 对某些属性的使用。这些不会 post 返回，因此如果您 return 视图（例如 ModelState 无效），则需要重新填充这些属性。或者，您可以生成只读文本框或为这些属性添加隐藏输入。我还建议您检查生成的 HTML，特别是看起来像

的名称属性

<input type="radio" name="Subjects[0].Questions[0].SelectedAnswer" ...

让您了解集合如何绑定到您的模型 post back

Answer 2

诀窍是使用一个表达式（Html.RadioButtonFor 的第一个参数），其中包含一个值，该值在每组单选按钮中发生变化。在您的情况下，它将是问题列表中的索引。

下面是一些示例代码：

 @for (int i = 0; i < Model.GeneralQuestions.Count; i++)
 {
     var question = Model.GeneralQuestions[i];
     @Html.Label(question.QuestionString)
     <br />
     foreach (var answer in question.PossibleAnswers)
     {
         @Html.RadioButtonFor(model => 
           Model.GeneralQuestions[i].SelectedAnswerId, answer.Id)
         @Html.Label(answer.Answer)
         <br />
     }
 }

这会产生以下结果 HTML：

<label for="Q1">Q1</label>
<br />
<input id="GeneralQuestions_0__SelectedAnswerId" 
  name="GeneralQuestions[0].SelectedAnswerId" type="radio" value="1" />
<label for="A01">A01</label>
<br />
<input id="GeneralQuestions_0__SelectedAnswerId" 
  name="GeneralQuestions[0].SelectedAnswerId" type="radio" value="2" />
<label for="A02">A02</label>
<br />
<label for="Q2">Q2</label>
<br />
<input id="GeneralQuestions_1__SelectedAnswerId" 
  name="GeneralQuestions[1].SelectedAnswerId" type="radio" value="11" />
<label for="A11">A11</label>
<br />
<input id="GeneralQuestions_1__SelectedAnswerId" 
  name="GeneralQuestions[1].SelectedAnswerId" type="radio" value="12" />
<label for="A12">A12</label>
<br />

为了完整起见，这里是所用模型的简化版本：

public class StudentViewModel
{
    public List<Question> GeneralQuestions { get; set; }
}

public class Question
{
    public int QuestionId { get; set; }
    public string QuestionString { get; set; }
    public ICollection<PossibleAnswer> PossibleAnswers { get; set; }
    public int SelectedAnswerId { get; set; }
}

public class PossibleAnswer
{
    public int Id { get; set; }
    public string Answer { get; set; }
}

这里是操作方法的代码：

return View(new StudentViewModel
{
    GeneralQuestions =
        new List<Question>
        {
            new Question
            {
                QuestionString = "Q1",
                PossibleAnswers =
                    new[]
                    {
                        new PossibleAnswer {Id = 1, Answer = "A01"},
                        new PossibleAnswer {Id = 2, Answer = "A02"}
                    }
            },
            new Question
            {
                QuestionString = "Q2",
                PossibleAnswers =
                    new[]
                    {
                        new PossibleAnswer {Id = 11, Answer = "A11"},
                        new PossibleAnswer {Id = 12, Answer = "A12"}
                    }
            },
        }
});

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