根据相关数据构建编辑视图模型

Question

我有一个应用程序来创建和编辑调查。每项调查都包含一组问题和相关答案（答案）。在创建调查时，问题集合将从单独的Questions表中生成。每年都会为每个使用同一组问题的用户创建一项新的调查问卷，以便随时间进行比较。

创建调查时，每个问题的答案都会保存下来，但是用户可能没有对每个问题给出答复，现在我必须构建一个视图来编辑现有答案。

模型

public class Survey 
{ 
    public int ID { get; set; } 
    public int AreaID { get; set; } 
    public Status Status { get; set; } 
    public DateTime AssessmentDate { get; set; } 
    public virtual Area Area { get; set; } 
    public virtual ICollection<Answer> Answers { get; set; } 
} 
public class Question 
{ 
    public int ID { get; set; } 
    public string QuestionText { get; set; } 
    public virtual ICollection<Answer> Answers { get; set; } 
} 
public class Answer 
{ 
    public int ID { get; set; } 
    public int? Response { get; set; } 
    public int QuestionID { get; set; } 
    public int SurveyID { get; set; } 
    public virtual Question Question { get; set; } 
    public virtual Survey Survey{ get; set; } 
} 

这里是我的视图模型，我用它来创建我的观点为编辑屏幕

public class SurveyResponseViewModel 
{ 
    public Assessment Assessment { get; set; } 
    public IEnumerable<Question> Questions { get; set; } 
} 

，并在GET方法的代码

public ActionResult Edit(int? id) 
{ 
    if (id == null) 
    { 
     return new HttpStatusCodeResult(HttpStatusCode.BadRequest); 
    } 
    Survey survey = db.Surveys.Find(id); 
    var viewModel = new SurveyResponseViewModel 
    { 
     Survey = survey, 
     Areas = new SelectList(db.Areas, "ID", "SubLevel").ToList(), 
     Questions = db.Questions.Where(q => q.isActive) 
    }; 
    if (survey == null) 
    { 
     return HttpNotFound(); 
    } 
    return View(viewModel); 
} 

这用所有问题填充我的视图模型，但每个问题都包含一组答案。如何在视图中仅显示和编辑与此调查相关的每个问题的答案？

@foreach (var question in Model.Questions) 
{ 
    // Display the question 
    @Html.Raw(question.QuestionText) 
    // How to create an input for the associated response?? 
    <input type="text" name="????" placeholder="Enter a number..." value="????" /> 
} 

注意，该响应是int?并且可以具有0和5之间的值（或null如果用户还没有给出的响应）。理想情况下，我希望将其渲染为单选按钮以选择可能的值。

Answer 1

首先，你需要创建代表一个问题，它的答案

public class QuestionVM 
{ 
    public int QuestionID { get; set; } 
    public string QuestionText { get; set; } 
    public int? AnswerID { get; set; } 
    [Range(0, 5)] 
    public int? Response { get; set; } 
} 

，主视图模型会（请注意，视图模型不应该包含在编辑时的一些数据模型属性）视图模型

public class SurveyResponseVM 
{ 
    public int ID { get; set; } // this will be bound by the route value 
    [Required(ErrorMessage = "Please select an area")] 
    [Display(Name = "Area")] 
    public int? SelectedArea { get; set; } 
    public IEnumerable<SelectListItem> AreaList { get; set; } 
    .... // other properties of assessment that you need for the view 
    public List<QuestionVM> Questions { get; set; } 
} 

所以，在视图中可以使用

@model SurveyResponseVM 
.... 
@using (Html.BeginForm()) 
{ 
    @Html.DropDownListFor(m => m.SelectedArea, Model.AreaList) 
    .... 
    for(int i = 0; i < Model.Questions.Count; i++) 
    { 
     <h3>@Model.Questions[i].QuestionText</h3> 
     @Html.HiddenFor(m => m.Questions[i].AnswerID) 
     for (int j = 0; j < 6; j++) 
     { 
      <label> 
       @Html.RadioButtonFor(m => m.Questions[i].Resonse, j, new { id = "" }) 
       <span>@j</span> 
      </label> 
     } 
    } 
    <input type="submit" value="Save" /> 
} 

这会后回

public ActionResult Edit(SurveyResponseVM model) 

对于GET方法得到的值，你的第二查询（db.Questions.Where(q => q.isActive)似乎不必要的，因为你已经拥有的Answer与Survey关联的集合（每个Answer包含Question财产。你的代码可以

Survey survey = db.Surveys.Find(id); 
if (survey == null) // check for null here 
{ 
    return HttpNotFound(); 
} 
IEnumerable<Area> areas = db.Areas; 
SurveyResponseVM model = new SurveyResponseVM() 
{ 
    ID = survey.ID, 
    SelectedArea = survey.AreaID, 
    .... // other properties of Survey as required for the view 
    AreaList = new SelectList(areas , "ID", "SubLevel"), 
    Questions = survey.Answers.Select(x => new QuestionVM() 
    { 
     QuestionText = x.Question.QuestionText, 
     AnswerID = x.ID, 
     Response = x.Response 
    }) 
}; 
return View(model);