隐式转换en C＃泛型类 [英] Implicit conversion en C# generic classes

问题描述

我有一个应用程序被构建为一个服务层，它使用一个存储库层来实现持久性。
我想创建一个泛型控制器类来重用共享行为，但我在尝试设置泛型参数时遇到了问题。以下代码：

  public class BusinessEntity 
 {} 
 
 public class Person：BusinessEntity 
 {} 
 
 public interface IRepository< T> T：BusinessEntity 
 {} 
 
 public interface IService< T，R> 
其中T：BusinessEntity 
其中R：IRepository< T> 
 {} 
 
公共部分接口IPersonRepository：IRepository< Person> 
 {} 
 
公共接口IPersonService：IService< Person，IPersonRepository> 
 {} 
 
公共抽象类BaseController< X，Y> 
其中X：BusinessEntity 
其中Y：IService< X，IRepository< X>> 
 {} 
 
 public class PersonController：BaseController< Person，IPersonService> 
 
 
 
 $ b $ p 
 $ b 
在编译时失败
 
 
类型 ConsoleApplication.IPersonService 不能在泛型类型或方法中使用类型参数 Y  C $ C> ConsoleApplication.BaseController< X，Y> 。不存在从 ConsoleApplication.IPersonService 到 ConsoleApplication.IService< ConsoleApplication.Person，ConsoleApplication.IRepository< ConsoleApplication.Person>>< code> 
 
 
 
此作品 
 
 
  public interface IPersonService： IService< Person，IRepository< Person>> 
  
但我失去了定制存储库
 
 
 
有一种方法可以让编译器实现 IPersonRepository 是 IRepository< Person> ？
解决方案
 
  public class BusinessEntity 
 {} 
 
 public class Person：BusinessEntity 
 {} 
 
 public interface IRepository< T> T：BusinessEntity 
 {} 
 
 public interface IService< T，R> 
其中T：BusinessEntity 
其中R：IRepository< T> 
 {} 
 
公共部分接口IPersonRepository：IRepository< Person> 
 {} 
 
公共接口IPersonService：IService< Person，IPersonRepository> 
 {} 
 
公共抽象类BaseController< X，Y，Z> 
其中X：BusinessEntity 
其中Y：IService< X，Z> 
其中Z：IRepository< X> 
 {} 
 
 public class PersonController：BaseController< Person，IPersonService，IPersonRepository> 
 {} 
  
解决您的评论：
 
 
 IPersonService可以扩展基本服务类以添加自定义设施，例如FindPersonsUnderAge（）。为此，它需要一个自定义存储库。实际上，LINQ避免了大量的自定义存储库代码，但有时它们是必需的。
 
 
无需IPersonService而不需要存储库类型是一个类型参数？例如： 
 
 
  public interface IService< T>其中T：BusinessEntity {} 
 
公共接口IPersonService：IService< Person> 
 {
 IEnumerable< Person> FindPersonsByAge（double minAge，double maxAge）; 
} 
 
公共类服务< T，R> ：IService< T> 
其中T：BusinessEntity 
其中R：IRepository< T> 
 {} 
 
 public class PersonService：Service< Person，IPersonRepository> ;, IPersonService 
 {} 
  
 
I have an application that is structured as an service layer wich uses a repository layer for persistence.
I'm trying to create a generic controller class to reuse shared behavior but I'm having trouble trying to set the generic parameters. The following code: 
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


The type ConsoleApplication.IPersonService cannot be used as type parameter Y in the generic type or method ConsoleApplication.BaseController<X,Y>. There is no implicit reference conversion from ConsoleApplication.IPersonService to ConsoleApplication.IService<ConsoleApplication.Person,ConsoleApplication.IRepository<ConsoleApplication.Person>>

this works
public interface IPersonService : IService<Person, IRepository<Person>>
but I lose the custom repository

There is a way to make the compiler realize IPersonRepository is an IRepository<Person>?
解决方案
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:

  
IPersonService can extend the base service class to add custom facilities, like FindPersonsUnderAge(). For this it requires a custom repository. Actually LINQ avoids a lot of custom repository code, but sometimes they are required.
Couldn't IPersonService do that without requiring the repository type to be a type parameter?  For example:
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
{ }


                        
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