Asp.Net核心1.1 ViewModel后形式后

Question

我有一个viewmodel我叫ResultsViewModel，我用它在asp.net核心mvc 1.1强烈类型我的创建视图。它有5个下拉菜单和在下面我的代码所示的几个输入字段：

这是视图模型

public class ResultsViewModel 
{ 
    public ResultsViewModel() 
    { 
    } 
    [Display(Name = "Students")] 
    public SelectList Students { get; set; } 
    [Display(Name = "Subjects")] 
    public SelectList Subjects { get; set; } 
    [Display(Name = "Term")] 
    public Term Terms { get; set; } 
    [Display(Name = "Continuous Assessment")] 
    public SelectList ContinuousAssessments { get; set; } 
    [Display(Name = "Continuous Assessment Score")] 
    [DisplayFormat(DataFormatString ="{0:F2}")] 
    public double CAScore { get; set; } 
    [Display(Name = "School Year")] 
    public SelectList Session { get; set; } 
    [Display(Name = "Class")] 
    public SelectList Class { get; set; } 
    [Display(Name = "Average Score")] 
    [DisplayFormat(DataFormatString = "{0:F2}")] 
    public double AverageScore { get; set; } 
    [Display(Name = "Term Total Score")] 
    [DisplayFormat(DataFormatString = "{0:F2}")] 
    public double TermTotal { get; set; } 
} 

这是创建视图。它有什么特别的

@model SwiftSchool.ViewModels.ResultsViewModel 
@{ 
    ViewData["Title"] = "Create"; 
} 
<h2>Create</h2> 
<form asp-action="Create" method="post"> 
    <div class="form-horizontal"> 
     <h4>Result</h4> 
     <hr /> 
     <div asp-validation-summary="ModelOnly" class="text-danger"></div> 
     <div class="form-group"> 
      <label asp-for="Students" class="col-md-2 control-label"></label> 
      <div class="col-md-10"> 
       @Html.DropDownList("Student", Model.Students, "Select Student", new { @class = "form-control", @id = "studentselect" }) 
      </div> 
     </div> 
     <div class="form-group"> 
      <label asp-for="Subjects" class="col-md-2 control-label"></label> 
      <div class="col-md-10"> 
       @Html.DropDownList("Subject", Model.Subjects, "Select Subject", new { @class = "form-control", @id = "subjectselect" }) 
      </div> 
     </div> 
     <div class="form-group"> 
      <label asp-for="Session" class="col-md-2 control-label"></label> 
      <div class="col-md-10"> 
       @Html.DropDownList("Session", Model.Session, "Select School Session", 
       new { @class = "form-control", @id = "sessionselect" }) 
      </div> 
     </div> 
     <div class="form-group"> 
      <label asp-for="Class" class="col-md-2 control-label"></label> 
      <div class="col-md-4"> 
       @Html.DropDownList("Class", Model.Class, "Select Student Class", 
       new { @class = "form-control", @id = "classselect" }) 
      </div> 
     </div> 
     <div class="form-group"> 
      <label asp-for="ContinuousAssessments" class="col-md-2 control-label"></label> 
      <div class="col-md-10"> 
       @Html.DropDownList("C.A", Model.ContinuousAssessments, "Select C.A", 
       new { @class = "form-control", @id = "caselect" }) 
      </div> 
     </div> 
     <div class="form-group"> 
      <label asp-for="CAScore" class="col-md-2 control-label"></label> 
      <div class="col-md-10"> 
       <input asp-for="CAScore" class="form-control" readonly id="cascore" /> 
       <span asp-validation-for="CAScore" class="text-danger" /> 
      </div> 
     </div> 
     <div class="form-group"> 
      <label asp-for="AverageScore" class="col-md-2 control-label"></label> 
      <div class="col-md-10"> 
       <input asp-for="AverageScore" class="form-control" /> 
       <span asp-validation-for="AverageScore" class="text-danger" /> 
      </div> 
     </div> 
     <div class="form-group"> 
      <label asp-for="TermTotal" class="col-md-2 control-label"</label> 
      <div class="col-md-10"> 
       <input asp-for="TermTotal" class="form-control" /> 
       <span asp-validation-for="TermTotal" class="text-danger" /> 
      </div> 
     </div> 
     <div class="form-group"> 
      <div class="col-md-offset-2 col-md-10"> 
       <input type="submit" value="Create" class="btn btn-default"/> 
      </div> 
     </div> 
    </div> 
</form> 
<div> 
    <a asp-action="Index">Back to List</a> 
</div> 
@section Scripts { 
    @{await Html.RenderPartialAsync("_ValidationScriptsPartial");} 
} 

标准我有形式提交和我ResultsViewModel回到我的控制器。创造我的看法和处理POST方法下拉两种方法如下所示：

// GET: Result/Create 
public IActionResult Create() 
{ 
    var rim = new ResultsViewModel(); 
    rim.Students = new SelectList(_context.Students.ToList(), "Id", "FullName"); 
    rim.Subjects = new SelectList(_context.Subjects.ToList(), "Id", "Name"); 
    rim.ContinuousAssessments = new SelectList(_context.ContinuousAssessment.ToList(), "Id", "Name"); 
    rim.Class = new SelectList(_context.Classes.ToList(), "Id", "ClassName"); 
    rim.Session = new SelectList(_context.Sessions.ToList(), "Id", "SessionName"); 
    return View(rim); 
} 
[HttpPost] 
[ValidateAntiForgeryToken] 
public async Task<IActionResult> Create(ResultsViewModel model) 
{ 
    if (ModelState.IsValid) 
    { 
     _context.Add(model); 
     await _context.SaveChangesAsync(); 
     return RedirectToAction("Index"); 
    } 

     return View(model); 
    } 
} 

所以，当我在表格上选择和填写所有字段后做形式的一个帖子，我设置一个断点，我检查ModelState是否有效，并检查注入到Create方法中的视图模型，并且一切都是空的，特别是下拉列表。所以一切都从那里往南走。有人能让我知道发生了什么吗？因为我觉得这很烦人。我希望这不是框架中的另一个错误，因为我发现这是早期版本框架中的一个错误。反正任何帮助将不胜感激。

Answer 1

您创建的下拉列表与模型中的任何属性都没有关系。

第一个绑定到名为Student的属性，该属性不存在。第二个绑定到名为Subject的属性，该属性再次不存在。第三个绑定到属性Session，这是一个复杂对象的集合（IEnumerable<SelectListItem>），但<select>元素仅回发一个值 - 选定选项的值。第四名同上。

你的模型需要的属性绑定到

[Display(Name = "Students")] 
[Required("Please select a student")] 
public int SelectedStudent { get; set; } 

public IEnumerable<SelectListItem> Students { get; set; } 

，然后在其

@Html.DropwDownListFor(m => m.SelectedStudent, Model.Students, "Select Student", new { @class = "form-control" }) 

注意，鉴于其目前还不清楚为什么您使用new { @id = "studentselect" }覆盖由该方法生成的默认id属性（它是id="SelectedStudent"）

Alter本地，使用标签助手

<select asp-for="SelectedStudent" asp-items="Model.Students" class="form-control"> 
    <option>Select Student</option> 
</select> 

使用将绑定精细假设你提交这些属性类型的有效值产生的3个输入。

边注：在POST方法，你需要你的模型返回视图之前重新填充SelectLists，否则将被null并且将引发异常 - 指The ViewData item that has the key 'XXX' is of type 'System.Int32' but must be of type 'IEnumerable'