如何使用DropDownListFor

傳遞一個對象我有一個教師評分系統。當我創建一個關於教師的新評論時，我有一個dropdownlistfor（）列表，可供學生選擇。我希望該下拉列表在提交時傳遞課程對象，但是它只是傳入null並給我一個錯誤。我正在使用一個viewbag來顯示所有可用的課程。如何使用DropDownListFor

型號：

public class TeachersRatingsWall 
{ 

    public int ID { get; set; } 



    [Range(1, 5, ErrorMessage = "Invalid rating")] 
    public Int32 StarRating { get; set; } 

    [Required] 
    public string PostComment { get; set; } 

    public DateTime PostDate { get; set; } 

    [Required] 
    public string Teacher { get; set; } //? or public Teacher Teacher { get; set; } 

    public Guid PosterID { get; set; } 

    public string PosterUserName { get; set; } 

    //[Required] 
    public Course Course { get; set; } 

    public Guid CourseID { get; set; } 




    } 
}

Ropository：

 public IQueryable<TeachersRatingsWall> Select() 
    { 
     return table.Select(x => new TeachersRatingsWall 
           { 
            ID = x.ID, 
            StarRating = x.StarRating, 
            PostComment = x.PostComment, 
            PostDate = x.PostDate, 
            Teacher = x.Teacher, 
            PosterID = x.PosterID, 
            CourseID = x.CourseID, 
            Course = new Course { 
             ID = x.CourseID, 
             CourseNumber = x.CourseEntity.CourseNumber, 
             Department = x.CourseEntity.Department, 
             Description = x.CourseEntity.Description, 
             Name = x.CourseEntity.Name 

                 } 

           }); 

    }

控制器：

public ActionResult Create() 

{ 

    ViewBag.allcourses = coursesservice.GetAllCoursesNamesAndNumbers().Select(x => x.Department + " " + x.CourseNumber); 

     //----------------------------------------------------------------------------------------------------------- 
     return View(); 
    } 


    [HttpPost] 
    public ActionResult Create(TeachersRatingsWall collection) 
    {   
     try 
     { 
      // TODO: Add insert logic here 
      collection.PosterID = ((Guid)Membership.GetUser().ProviderUserKey); 
      collection.PostDate = System.DateTime.Now; 

      teacherratingservice.CreateComment(collection); 
      return RedirectToAction("Index"); 
     } 
     catch 
     { 
      return View(); 
     } 
    }

視圖 - Create.cshtml

 <div class="editor-label"> 
     @Html.Label("Course:") 
    </div> 
    <div class="editor-field"> 
     @Html.DropDownListFor(model => model.Course, new SelectList(ViewBag.allcourses)) 

    </div>

來源

2012-03-05 TMan

你的模型必須滿足下列條件

public int CourseId { get; set; }

和

public IList<SelectListItem> Courses { get; set; }

在你的控制，你必須填寫這兩個模型物品放在一起，然後在你看來，應該是這樣的

@Html.DropDownListFor(model => model.CourseId, Model.Courses, "")

MVC將自動爲您映射併爲GET和POST選擇必要的項目

來源

2012-03-05 03:05:38 Raymund

IQueryable Select（）中的所有內容看起來都不錯嗎？ – TMan 2012-03-05 03:08:44

給我在IList的SelectListItem錯誤..任何想法爲什麼？名稱空間或類型無法找到它說 – TMan 2012-03-05 03:10:27

是的，你需要改變它填充Model.Courses這就是爲什麼它給你一個錯誤 – Raymund 2012-03-05 03:13:33

如何使用DropDownListFor

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