[英]Implicit conversion en C# generic classes
I have an application that is structured as an service layer wich uses a repository layer for persistence. 我有一个结构化为服务层的应用程序,它使用存储库层来实现持久性。 I'm trying to create a generic controller class to reuse shared behavior but I'm having trouble trying to set the generic parameters.
我正在尝试创建一个通用控制器类来重用共享行为,但我在设置泛型参数时遇到了麻烦。 The following code:
以下代码:
public class BusinessEntity
{ }
public class Person : BusinessEntity
{ }
public interface IRepository<T> where T : BusinessEntity
{ }
public interface IService<T, R>
where T : BusinessEntity
where R : IRepository<T>
{ }
public partial interface IPersonRepository : IRepository<Person>
{ }
public interface IPersonService : IService<Person, IPersonRepository>
{ }
public abstract class BaseController<X, Y>
where X : BusinessEntity
where Y : IService<X, IRepository<X>>
{ }
public class PersonController : BaseController<Person, IPersonService>
{ }
fails at compilation with 编译失败
The type ConsoleApplication.IPersonService
cannot be used as type parameter Y
in the generic type or method ConsoleApplication.BaseController<X,Y>
. ConsoleApplication.IPersonService
类型不能用作泛型类型或方法ConsoleApplication.BaseController<X,Y>
中的类型参数Y
There is no implicit reference conversion from ConsoleApplication.IPersonService
to ConsoleApplication.IService<ConsoleApplication.Person,ConsoleApplication.IRepository<ConsoleApplication.Person>>
从
ConsoleApplication.IPersonService
到ConsoleApplication.IService<ConsoleApplication.Person,ConsoleApplication.IRepository<ConsoleApplication.Person>>
没有隐式引用转换。
this works 这很有效
public interface IPersonService : IService<Person, IRepository<Person>>
but I lose the custom repository 但我失去了自定义存储库
There is a way to make the compiler realize IPersonRepository
is an IRepository<Person>
? 有一种方法可以使编译器实现
IPersonRepository
是一个IRepository<Person>
?
public class BusinessEntity
{ }
public class Person : BusinessEntity
{ }
public interface IRepository<T> where T : BusinessEntity
{ }
public interface IService<T, R>
where T : BusinessEntity
where R : IRepository<T>
{ }
public partial interface IPersonRepository : IRepository<Person>
{ }
public interface IPersonService : IService<Person, IPersonRepository>
{ }
public abstract class BaseController<X, Y, Z>
where X : BusinessEntity
where Y : IService<X, Z>
where Z : IRepository<X>
{ }
public class PersonController : BaseController<Person, IPersonService, IPersonRepository>
{ }
To address your comment: 解决你的评论:
IPersonService can extend the base service class to add custom facilities, like FindPersonsUnderAge().
IPersonService可以扩展基本服务类以添加自定义工具,如FindPersonsUnderAge()。 For this it requires a custom repository.
为此,它需要一个自定义存储库。 Actually LINQ avoids a lot of custom repository code, but sometimes they are required.
实际上LINQ避免了很多自定义存储库代码,但有时它们是必需的。
Couldn't IPersonService do that without requiring the repository type to be a type parameter? 如果不要求存储库类型是类型参数,IPersonService能不能这样做吗? For example:
例如:
public interface IService<T> where T : BusinessEntity { }
public interface IPersonService : IService<Person>
{
IEnumerable<Person> FindPersonsByAge(double minAge, double maxAge);
}
public class Service<T, R> : IService<T>
where T : BusinessEntity
where R : IRepository<T>
{ }
public class PersonService : Service<Person, IPersonRepository>, IPersonService
{ }
Thanks to sll for pointing me in the right direction 感谢sll指出我正确的方向
public interface IService<T, out R>
where T : BusinessEntity
where R : IRepository<T>
{ }
does the trick 诀窍
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