MVC 多选不会返回 ViewModel 中的选定项目

Question

我很难让我的 MVC 5 多选控件返回 ViewModel 中的选定项目。就好像选定的列表框项没有绑定到可用的 EmployeeCategoriesId 集合，导致返回集合始终为空。

视图模型

public class EmployeeCreateViewModel
{
    [Required]
    public long OrganizationId { get; set; }

    [Display(Name = "FirstName", ResourceType = typeof(Resources.Resources))]
    [Required(ErrorMessageResourceType = typeof(Resources.Resources), ErrorMessageResourceName = "FirstNameRequired")]
    public string FirstName { get; set; }

    [Display(Name = "LastName", ResourceType = typeof(Resources.Resources))]
    [Required(ErrorMessageResourceType = typeof(Resources.Resources), ErrorMessageResourceName = "LastNameRequired")]
    public string LastName { get; set; }

    [Display(Name = "DateOfBirth", ResourceType = typeof(Resources.Resources))]
    [Required(ErrorMessageResourceType = typeof(Resources.Resources), ErrorMessageResourceName = "DateOfBirthRequired")]
    public DateTime? DOB { get; set; }

    //Employee categories selected from multi select list
    public IEnumerable<int> EmployeeCategoriesId { get; set; }

    //Employee categories for multi select list
    [Display(Name = "Department", ResourceType = typeof(Resources.Resources))]
    public List<EmployeeCategoryDefinition> SelectEmployeeCategories { get; set; }
}

控制器

// GET: Employees/Create
    public ActionResult Create()
    {
        long organizationId = Convert.ToInt64(User.Identity.GetOrganizationId());

        EmployeeCreateViewModel employeeCreateViewModel = new EmployeeCreateViewModel();

        employeeCreateViewModel.SelectEmployeeCategories = db.EmployeeCategoryDefinition
                                                            .Where(ecat => ecat.OrganizationId == organizationId)
                                                            .OrderBy(ecat => ecat.Name)
                                                            .ToList();

        return View(employeeCreateViewModel);
    }

    // POST: Employees/Create
    // To protect from overposting attacks, please enable the specific properties you want to bind to, for 
    // more details see http://go.microsoft.com/fwlink/?LinkId=317598.
    [HttpPost]
    [ValidateAntiForgeryToken]
    public async Task<ActionResult> Create([Bind(Include = "Id,OrganizationId,FirstName,LastName,DOB,CreatedUTC")] EmployeeCreateViewModel employeeCreateViewModel)
    {
        if (ModelState.IsValid)
        {
            Employee employee = new Employee(employeeCreateViewModel);
            db.Employee.Add(employee);
            await db.SaveChangesAsync();
            return RedirectToAction("Index");
        }

        //Get Employee categories from DB - List binding lost at post back
        long organizationId = Convert.ToInt64(User.Identity.GetOrganizationId());
        employeeCreateViewModel.SelectEmployeeCategories = db.EmployeeCategoryDefinition
                                                    .Where(ecat => ecat.OrganizationId == organizationId)
                                                    .OrderBy(ecat => ecat.Name)
                                                    .ToList();

        return View(employeeCreateViewModel);
    }

视图（包含在 BeginForm 中）

<div class="col-sm-10">
            @Html.ListBoxFor(m => m.EmployeeCategoriesId,
                             new MultiSelectList(Model.SelectEmployeeCategories, "Id", "Name"),
                             new { @class = "chosen-select", @style = "width:350px;", @data_placeholder = "PH" })  
</div>

你能明白为什么我的 ViewModel 中返​​回的“EmployeeCategoriesId”总是返回 null 给 POST 控制器操作吗？ ListBox 会填充传递给视图的选项。

Answer 1

您有一个 [Bind(Include="..")] 属性，该属性专门从绑定中排除了属性 EmployeeCategoriesId。

由于您使用的是视图模型，它应该只代表您要在视图中编辑的属性，因此您甚至不应该包含BindAttribute（默认情况下所有属性都已绑定）