Question

我在使用所有IEnumerable对象时得到Only primitive types or enumeration types are supported in this context ...我不知道这里有什么问题。这是我的模特：

public class UserRoleViewModel
{
    public string Name { get; set; }
    public bool IsChecked { get; set; }

}
public class UserRoleEditViewModel
{

    [DisplayName("Id")]
    public int Id { get; set; }

    [DisplayName("User Name")]
    public string UserName { get; set; }

    [DisplayName("User Roles")]
    public IEnumerable<UserRoleViewModel> UserRoles { get; set; }

}

这是控制器：

 public ActionResult Edit(int? id)
    {
        if (id == null)
        {
            return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
        }
        User user = db.Users.Find(id);
        if (user == null)
        {
            return HttpNotFound();
        }

        UserRoleEditViewModel model = new UserRoleEditViewModel
        {                
            UserName = user.UserName,
            Id = user.Id,
            UserRoles = db.UserRoles.Select(x=> new UserRoleViewModel(){Name = x.RoleName, IsChecked = x.Users.Contains(user)}).AsEnumerable()                
        };

        return View(model);
    }

观点：

            @foreach (var userRoleViewModel in Model.UserRoles)//<ERR
            {
                <div>
                    @Html.Hidden(userRoleViewModel.Name)
                    @Html.CheckBox(userRoleViewModel.IsChecked.ToString())
                    @Html.Label(userRoleViewModel.Name, userRoleViewModel.Name)
                </div>
            }
        </div>

也尝试了这个：

 @for (int i = 0; i < Model.UserRoles.Count(); i++) //<ERR
            {                    
                <div>
                    @Html.Hidden(Model.UserRoles.ToList()[i].Name)
                    @Html.CheckBox(Model.UserRoles.ToList()[i].IsChecked.ToString())
                    @Html.LabelFor(x => x.UserRoles.ToList()[i].IsChecked, Model.UserRoles.ToList()[i].Name)
                </div>
            }

我的视图模型都是IEnumerable＆＃39; d ...所以，我不知道这里有什么问题。

以上标有＆＃34; //的行

也不是

@foreach（Model.UserRoles中的var userRoleViewModel）

Answer 1

我假设您的错误可能在这里：

UserRoles = db.UserRoles.Select(x=> 
    new UserRoleViewModel(){Name = x.RoleName, IsChecked = x.Users.Contains(user)})
    .AsEnumerable()

问题是你无法在SQL中翻译它。没有SQL语句可以构造您的UserRoleViewModel对象。因此，您需要做的是首先从数据库中选择所需的数据，然后使用它来构建对象。例如，像这样：

// You can create anonymous types in LINQ to SQL, so do that first
UserRoles = db.UserRoles.Select(x => new { x.RoleName, IsChecked = x.Users.Contains(user) })
    .ToList()    // this forces the database to actually return data
    // Now we can actually construct your object because we aren't doing on the database
    .Select(x => new UserRoleViewModel() { Name = x.RoleName, IsChecked = x.IsChecked });

Answer 2

仅供参考，我最后做了这个丑陋的事情：

  List<UserRoleViewModel> vmList = new List<UserRoleViewModel>();
        foreach (var userRole in db.UserRoles)
        {
            UserRoleViewModel urVM = new UserRoleViewModel()
            {
                Name = userRole.RoleName
            };

            if (user.UserRoles.Contains(userRole))
                urVM.IsChecked = true;
            else
                urVM.IsChecked = false;

            vmList.Add(urVM);
        }

        model.UserRoles = vmList;

使用IEnumerable对象在此上下文中仅支持原始类型或枚举类型

2 个答案: