Question

我正在为我的MVC 4项目构建（尝试构建）通用存储库，任务和控制器，并使用它来学习泛型和接口。我已经走得很远，但坚持这个错误。 CustomerContactsListViewModel继承自IViewModelList，这就是为什么我感到困惑。

错误：

The type 'OTIS.AppServ.OrderMgmt.ViewModels.CustomerContactsListViewModel' cannot be used as type parameter 'TViewModelList' in the generic type or method 'OTIS.AppServ.BaseAppServGrid<TRepository,TViewModelSingle,TViewModelList>'. There is no implicit reference conversion from 'OTIS.AppServ.OrderMgmt.ViewModels.CustomerContactsListViewModel' to 'OTIS.AppServ.IViewModelList<OTIS.domain.OrderMgmt.Customer,OTIS.AppServ.OrderMgmt.ViewModels.CustomerContactsListViewModel>'.

界面：

public interface IViewModelList<TClass, TViewModelList>
    {
        IEnumerable<TClass> ConvertViewModelToClass(IEnumerable<TViewModelList> entityList);
        IEnumerable<TViewModelList> ConvertClassToViewModel(IEnumerable<TClass> entityList);
    }

继承接口的视图模型：

    public class CustomerContactsListViewModel : IViewModelList<CustomerContact, CustomerContactsListViewModel>, IEntity

继承的通用任务（应用程序服务）类：

public class BaseAppServGrid<TRepository, TViewModelSingle, TViewModelList> : BaseAppServ<TRepository, TViewModelSingle>
            where TRepository : class, IEntity, IAuditStamps, new()
            where TViewModelSingle : class, IViewModelSingle<TRepository, TViewModelSingle>, new()
            where TViewModelList : class, IEntity, IViewModelList<TRepository, TViewModelList>, new()

尝试继承Base的特定Task / App服务类会抛出错误：

public class ManageCustomersAppServ : BaseAppServGrid<Customer, CustomerViewModel, CustomerContactsListViewModel>

Answer 1

在CustomerContactsListViewModel中，您已将IViewModelList的第一个参数实现为CustomerContact类型。

但是，已使用ManageCustomersAppServ类型声明了类Customer。

所以

IViewModelList<Customer, CustomerContactsListViewModel>

不能转发给

IViewModelList<CustomerContact, CustomerContactsListViewModel>

您需要：

更改BaseAppServGrid以采用其他通用参数：

public class BaseAppServGrid<TModel, TRepository, TViewModelSingle, TViewModelList> :
    BaseAppServ<TRepository, TViewModelSingle>
    where TRepository : class, IEntity, IAuditStamps, new()
    where TViewModelSingle : class, IViewModelSingle<TRepository, TViewModelSingle>, new()
    where TViewModelList : class, IEntity, IViewModelList<TModel, TViewModelList>, new()

public class ManageCustomersAppServ : BaseAppServGrid<CustomerContact, Customer, CustomerViewModel, CustomerContactsListViewModel>

检查Customer 和 CustomerContact是否可以从某个IRepository接口/类派生，如果您将Customer传递给名为“TRepository”的通用参数，那么这是您的意图。
< / LI>

类不能在泛型类型或方法中用作类型参数，也没有隐式引用转换

1 个答案: