[英]How to inject dependencies of generics in ASP.NET Core
I have following repository classes:我有以下存储库类:
public class TestRepository : Repository<Test>
{
private TestContext _context;
public TestRepository(TestContext context) : base(context)
{
_context = context;
}
}
public abstract class Repository<T> : IRepository<T> where T : Entity
{
private TestContext _context;
public Repository(TestContext context)
{
_context = context;
}
...
}
public interface IRepository<T>
{
...
}
How do I implement the dependency injection in ASP.NET Core in my Startup.cs
?如何在
Startup.cs
ASP.NET Core 中实现依赖注入?
I implemented it like this:我是这样实现的:
services.AddScoped(typeof(IRepository<>), typeof(Repository<>));
But then I get following error:但后来我收到以下错误:
Cannot instantiate implementation type 'Test.Domain.Repository
1[T]' for service type 'Test.Domain.IRepository
1[T]'.无法
1[T]' for service type 'Test.Domain.IRepository
1[T]”实例化实现类型“1[T]' for service type 'Test.Domain.IRepository
1[T]”。
Repository<T>
is an abstract class, so you cannot register it as an implementation, because abstract class simply cannot be instantiated. Repository<T>
是一个抽象类,所以你不能将它注册为一个实现,因为抽象类根本不能被实例化。 Your registration would work fine if Repository<T>
was not abstract.如果
Repository<T>
不是抽象的,您的注册就可以正常工作。
If you cannot make repository class non-abstract, you can register specific implementation of your repository class:如果您不能使存储库类成为非抽象类,则可以注册存储库类的特定实现:
services.AddScoped(typeof(IRepository<Test>), typeof(TestRepository));
This will correctly inject dependencies to your controller.这将正确地将依赖项注入您的控制器。
I know this is very late but I am posting my solution here so that others can refer and use this.我知道这已经很晚了,但我在这里发布了我的解决方案,以便其他人可以参考和使用它。 I have written some extensions to register all the derived types of generic interface.
我编写了一些扩展来注册泛型接口的所有派生类型。
public static List<TypeInfo> GetTypesAssignableTo(this Assembly assembly, Type compareType)
{
var typeInfoList = assembly.DefinedTypes.Where(x => x.IsClass
&& !x.IsAbstract
&& x != compareType
&& x.GetInterfaces()
.Any(i => i.IsGenericType
&& i.GetGenericTypeDefinition() == compareType))?.ToList();
return typeInfoList;
}
public static void AddClassesAsImplementedInterface(
this IServiceCollection services,
Assembly assembly,
Type compareType,
ServiceLifetime lifetime = ServiceLifetime.Scoped)
{
assembly.GetTypesAssignableTo(compareType).ForEach((type) =>
{
foreach (var implementedInterface in type.ImplementedInterfaces)
{
switch (lifetime)
{
case ServiceLifetime.Scoped:
services.AddScoped(implementedInterface, type);
break;
case ServiceLifetime.Singleton:
services.AddSingleton(implementedInterface, type);
break;
case ServiceLifetime.Transient:
services.AddTransient(implementedInterface, type);
break;
}
}
});
}
In the startup class, you just register your generic interface like below.在启动类中,您只需注册您的通用接口,如下所示。
services.AddClassesAsImplementedInterface(Assembly.GetEntryAssembly(), typeof(IRepository<>));
You can find the complete extension code in this Github repository.您可以在此Github存储库中找到完整的扩展代码。
You can register an abstract class only as a service , not as implementation as @dotnetom said.您只能将抽象类注册为服务,而不是@dotnetom 所说的实现。
See the definitions below请参阅下面的定义
public abstract class BaseClass<T>
{
public BaseClass()
{
}
}
public class DerivedClass : BaseClass<Entity>
{
public DerivedClass() : base() { }
}
public class DerivedClass2<T> : BaseClass<T> where T: Entity
{
}
public class Entity
{
}
Controller:控制器:
public class WeatherForecastController : ControllerBase
{
......
public WeatherForecastController(BaseClass<Entity> baseClass)
{
}
...
}
If you inject them on this way:如果您以这种方式注入它们:
services.AddScoped(typeof(BaseClass<>), typeof(DerivedClass));
you get this error when you are resolving your dependency:解决依赖项时会收到此错误:
Open generic service type 'BaseClass`1[T]' requires registering an open generic implementation type.
开放的通用服务类型“BaseClass`1[T]”需要注册一个开放的通用实现类型。 (Parameter 'descriptors')
(参数“描述符”)
You should register the generic type or register the service and the implementation with the generic argument defined您应该注册泛型类型或使用定义的泛型参数注册服务和实现
Now this should work perfectly as well现在这也应该可以完美运行
services.AddScoped(typeof(BaseClass<>), typeof(DerivedClass2<>));
or或
services.AddScoped(typeof(BaseClass<Entity>), typeof(DerivedClass2<Entity>));
IMHO I prefer to go with interface definitions rather than abstract classes.恕我直言,我更喜欢使用接口定义而不是抽象类。
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