从Dropdownlist绑定SelectedItem到模型对象在MVC 4

Question

我很新的MVC，所以忍受我，但我似乎无法绑定一个选择列表中的值到选定对象的实例在回发期间MVC 4.

假设我必须创建一位教师作为学校的成员。我有一个ViewModel类定义为这样：

public class RegisterTeacherModel 
{ 
    [Required] 
    [Display(Name = "User name")] 
    public string UserName { get; set; } 

    [Required] 
    [DataType(DataType.EmailAddress)] 
    [Display(Name = "Email address")] 
    public string Email { get; set; } 

    [Required] 
    [Display(Name = "School")] 
    public School SelectedSchool { get; set; } 

    [ScaffoldColumn(false)] 
    public Guid UserId 
    { 
     get; 
     set; 
    } 

    public SelectList PossibleSchools 
    { 
     get; 
     private set; 
    } 

    public RegisterTeacherModel(IRepository<School> schoolRepo) 
    { 
     PossibleSchools = new SelectList(schoolRepo, "Id", "Name"); 
    } 
} 

而我的观点：

@using (Html.BeginForm()) { 
@Html.ValidationSummary(true) 

<fieldset> 
    <legend>RegisterTeacherModel</legend> 

    <div class="editor-label"> 
     @Html.LabelFor(model => model.UserName) 
    </div> 

    <div class="editor-label"> 
     @Html.LabelFor(model => model.Email) 
    </div> 
    <div class="editor-field"> 
     @Html.EditorFor(model => model.Email) 
     @Html.ValidationMessageFor(model => model.Email) 
    </div> 

    <div class="editor-label"> 
     @Html.LabelFor(model => model.SelectedSchool) 
    </div> 
    <div class="editor-field"> 
     @Html.DropDownListFor(model => model.SelectedSchool, Model.PossibleSchools) 
    </div> 
    <p> 
     <input type="submit" value="Create" /> 
    </p> 
</fieldset> 
} 

最后，我的控制器方法：

[HttpPost, ActionName("Create")] 
    public ActionResult CreateTeacher(RegisterTeacherModel teacherModel) 
    { 
     if (ModelState.IsValid) 
     { 
      try 
      { 
       ... 
      } 
     } 
    } 

但是，当我收到RegisterTeacherModel对象回我的控制器中的Create方法，SelectedSchool始终为空。我必须以模型绑定器在回发中重新创建对象引用的方式丢失一些东西。任何人都可以将我指向正确的方向吗？

Answer 1

嗯，我找到了解决方法。我仍然不知道如果我失去了一些东西，但不是在我的ViewModel使用学校的对象，我与SelectedSchoolId这样取代了它：

public class RegisterTeacherModel 
{ 
    [Required] 
    [Display(Name = "User name")] 
    public string UserName { get; set; } 

    [Required] 
    [DataType(DataType.EmailAddress)] 
    [Display(Name = "Email address")] 
    public string Email { get; set; } 

    [Required] 
    [Display(Name = "School")] 
    public int SelectedSchoolId { get; set; } 

    ... 
} 

而改变我的查看下拉菜单，而不是使用这样的：

<div class="editor-field"> 
    @Html.DropDownListFor(model => model.SelectedSchoolId, Model.PossibleSchools) 
</div> 

然后在我的控制器，创造真正的模型对象时，我可以简单地拉离学校资源库的学校对象，并将其与真正的老师对象相关联。

Answer 2

我想你在第二篇文章中谈到了它：尝试将初始代码指向Model.SelectedSchool。 <IdProperty>

<div class="editor-field"> 
    @Html.DropDownListFor(model => model.SelectedSchool.**<IdProperty>**, Model.PossibleSchools) 
</div>