如何使用DropDownListFor當模型是列表

Question

我的模型是一個通用的列表。我想使用DropDownList作爲外鍵屬性綁定。 我的代碼是

型號

public class PersonViewModel 
{ 
    public int Id { get; set; } 
    public string LastName{get;set;} 
    public int NationalityId { get; set; } 
} 

public class Nationality 
{ 
    public int Id { get; set; } 
    public string Name { get; set; } 
} 

控制器

public ActionResult Index() 
{ 

    var nationalities = new List<Nationality> 
    { 
     new Nationality{Id = 0, Name = "CHOOSE NATIONALITY..."}, 
     new Nationality{Id = 1, Name = "POLAND"}, 
     new Nationality{Id = 2, Name = "USA"}, 
     new Nationality{Id = 3, Name = "CANADA"} 
    }; 


    var Nationalities = new SelectList(nationalities, "Id", "Name"); 


    var persons = new List<PersonViewModel> 
    { 
     new PersonViewModel{Id = 1, LastName = "KOWALSKI", NationalityId = 1}, 
     new PersonViewModel{Id = 1, LastName = "SMITH", NationalityId = 2}, 
     new PersonViewModel{Id = 1, LastName = "SCHERBATSKY", NationalityId = 3} 
    }; 

    ViewBag.Nationalities = Nationalities; 

    return View(persons); 
} 

查看

@model List<PersonViewModel> 

@Html.EditorFor(m=> Model[0].LastName) 
@Html.DropDownListFor(m => Model[0].NationalityId, (SelectList)ViewBag.Nationalities) 

@Html.EditorFor(m => Model[1].LastName) 
@Html.DropDownListFor(m => Model[1].NationalityId, (SelectList)ViewBag.Nationalities) 

@Html.EditorFor(m => Model[2].LastName) 
@Html.DropDownListFor(m => Model[2].NationalityId, (SelectList)ViewBag.Nationalities) 

任何人都可以告訴我爲什麼NationalityId屬性不綁定以及

我無法上傳圖片，但它根本沒有任何約束力。每個DropDownList都有'選擇國籍...'。

Answer 1

我會使用編輯器模板建議您： 首先 - 創建查看Shared\EditorTemplates\PersonViewModel.cshtml包含：

兩

@model PersonViewModel 

@Html.EditorFor(m => Model.LastName) 
@Html.DropDownListFor(m => Model.NationalityId, (SelectList)ViewBag.Nationalities) 

而在當前視圖

@for (int i = 0; i < Model.Count; i++) 
{ 
    @Html.EditorFor(x => Model[i]) 
} 

Answer 2

更改您的視圖模型這個

public class PersonViewModel 
{ 
    public int Id { get; set; } 
    public string LastName{get;set;} 
    public int NationalityId { get; set; } 
    public IEnumerable<Nationality> Nationalities {get;set;} 
} 

在你的控制器

public ActionResult Index() 
{ 

    var nationalities = new List<Nationality> 
    { 
     new Nationality{Id = 0, Name = "CHOOSE NATIONALITY..."}, 
     new Nationality{Id = 1, Name = "POLAND"}, 
     new Nationality{Id = 2, Name = "USA"}, 
     new Nationality{Id = 3, Name = "CANADA"} 
    }; 


    var nationalities = new SelectList(nationalities, "Id", "Name"); 


    var persons = new List<PersonViewModel> 
    { 
     new PersonViewModel{Id = 1, LastName = "KOWALSKI", NationalityId = 1 , Nationalities = nationalities}, 
     new PersonViewModel{Id = 1, LastName = "SMITH", NationalityId = 2, Nationalities = nationalities}, 
     new PersonViewModel{Id = 1, LastName = "SCHERBATSKY", NationalityId = 3, Nationalities = nationalities} 
    };  
    return View(persons); 
} 

而且在你看來

@model List<PersonViewModel> 

@Html.EditorFor(m => m[0].LastName) 
@Html.DropDownListFor(m => m[0].NationalityId, Model[0].Nationalities) 

@Html.EditorFor(m => m[1].LastName) 
@Html.DropDownListFor(m => m[1].NationalityId, Model[1].Nationalities) 

@Html.EditorFor(m => m[2].LastName) 
@Html.DropDownListFor(m => m[2].NationalityId, Model[2].Nationalities) 

Answer 3

兩件事情：

1. 每個下拉菜單需要自己選擇列表中。目前，您每個下拉列表都使用相同的選擇列表。

2. 你需要爲每個選擇列表中指定一個選擇的值，就像這樣：

   new SelectList(nationalities, "Id", "Name", persons[0].NationalityId);