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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。我已经走了很远，但坚持这个错误。CustomerContactsListViewModel 确实继承自 IViewModelList，这就是我感到困惑的原因。

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

被继承的通用任务（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 服务类会引发错误：

public class ManageCustomersAppServ : BaseAppServGrid<Customer, CustomerViewModel, CustomerContactsListViewModel>
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1 回答 1

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在CustomerContactsListViewModel您已经实现了IViewModelList类型的第一个参数CustomerContact。

但是，该类ManageCustomersAppServ已使用 type 声明Customer。

所以

IViewModelList<Customer, CustomerContactsListViewModel>

不可分配给

IViewModelList<CustomerContact, CustomerContactsListViewModel>

您需要：

  1. Change BaseAppServGrid to take another generic parameter like so:

    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>

  2. Review whether Customer and CustomerContact can derive from some IRepository interface/class, if that was your intention when you passed Customer to a generic param called "TRepository".

于 2013-01-02T01:16:58.577 回答