ASP.NET MVC视图模型不绑定在HTTP Post with DropDownList

Question

我有一个问题，当我发布到控制器时，我失去了绑定，并且我的视图模型中的所有内容都是NULL。这里是我使用的代码：

查看：

@model ArticleCategoryVm 

@using (@Html.BeginForm()) 
{ 
    @Html.HiddenFor(model => model.LanguageIdDisplayed) 

    <label>Name: <span class="label label-important">Required</span></label> 
    @Html.HmlValidationFor(model => model.CategoryName) 
    @Html.TextBoxFor(model => model.CategoryName, new { maxlength = "255", placeholder = "Category Name", @class = "input-xlarge-fluid" })     
    <span class="help-block">The is the name of the category and how it appears on the site.</span> 

    <label>Language: <span class="label label-important">Required</span></label> 
    @Html.HmlValidationFor(model => model.LanguageId) 
    @Html.DropDownList("LanguageId", new SelectList(@Model.Languages, "Value", "Text"), "Select language", new { @class="input-xlarge-fluid" }) 
    <span class="help-block">This will be the language that the category is set too.</span> 

    <label>Parent:</label> 
    @Html.HmlValidationFor(model => model.CategoryParentId) 
    @Html.DropDownList("CategoryParentId", new SelectList(@Model.CategoryParents, "Value", "Text"), new { @class = "input-xlarge-fluid" }) 
    <span class="help-block">Allows you to group the category under another existing category.</span> 

    <label>Moderator Email: <span class="label label-important">Required</span></label> 
    @Html.HmlValidationFor(model => model.ModeratorEmail) 
    @Html.TextBoxFor(model => model.ModeratorEmail, new { maxlength = "255", placeholder = "Email Address", @class = "input-xlarge-fluid" }) 
    <span class="help-block">This is the moderator email for articles in this category.</span> 

    <button type="submit" class="btn btn-duadua btn-small"><i class="icon-ok-3"></i> Add New Category</button>      
} 

视图模型：

public class ArticleCategoryVm : BaseLayoutVm 
{ 
    public int LanguageIdDisplayed; 
    public List<ArticleCategoryItemVm> ArticleCategoryItemVms { get; set; } 

    // Add Category Fields 
    [Required] 
    public string CategoryName; 

    [EmailAttribute] 
    [Required] 
    public string ModeratorEmail; 

    [Required] 
    public int LanguageId; 

    public int CategoryParentId; 

    public List<SelectListItem> Languages { get; set; } 
    public List<SelectListItem> CategoryParents { get; set; } 
} 

控制器：

[HttpPost] 
public ActionResult Categories(ArticleCategoryVm vm) 
{ 
    // Code here 
    if (ModelState.IsValid) 
    { 
    } 

    ReDrawDropDowns(vm); 
    return View(vm) 
} 

为什么我的viewmodel中的所有内容都是NULL？我可以使用在博文的值被公布为字符串和整数铬合金工具看......作为一种解决我刚才做了以下获得代码工作：

解决方法控制器：

[HttpPost] 
public ActionResult Categories(int LanguageIdDisplayed, string CategoryName, string ModeratorEmail, int LanguageId, int CategoryParentId) 
{ 
    var vm = new ArticleCategoryVm() 
    { 
     CategoryName = CategoryName, 
     LanguageIdDisplayed = LanguageIdDisplayed, 
     ModeratorEmail = ModeratorEmail, 
     LanguageId = LanguageId, 
     CategoryParentId = CategoryParentId 
    }; 

    if (ModelState.IsValid) 
    { 
    } 

    ReDrawDropDowns(vm); 
    return View(vm) 
} 

感谢

Answer 1

貌似在this question指出这可能是因为属性和变量之间的差异。将{ get; set; }添加到您想要绑定的所有变量。正如在这个问题中指出的，我认为这是因为默认模型联编程序使用反射的方式。

我发现它实际上抓住了ASP.NET MVC源代码，因此我可以调试它并查看正在发生的事情。

Answer 2

要查看模型绑定，你应该使用strongly-typed-html-helpers

更换

@Html.DropDownList("CategoryParentId", new SelectList(@Model.CategoryParents, "Value", "Text"), new { @class = "input-xlarge-fluid" }) 

到：

@Html.DropDownListFor(model => model.CategoryParentId, new SelectList(@Model.CategoryParents, "Value", "Text"), new { @class = "input-xlarge-fluid" }) 

Answer 3

还有另一个原因为视图模型是NULL：

• 在动作参数模型的名称是相同的视图模型的属性

---

实施例中的一种：

型号：

public class NewBookPageView{ 
    int blabla {get;set;} 
    Book NewBook {get;set;} //NewBook is the same as newBook in action parameter 
} 

控制器：

[HttpPost] 
public ActionResult AddNewBook(NewBookPageView newBook)//newBook is the same as NewBook in view 
{ 
    int temp = newBook.blabla; 
    temp++; 
    //... 
} 

---

提示：这里相同名字的意思是不区分大小写（ newBook是相同 NewBook）

提示：面对在MVC3中d MVC4。