无法在.NET Core中注册嵌套的通用接口 [英] Cannot register nested generic interface in .NET Core

问题描述

我正在尝试在DI容器中注册嵌套的泛型类型，但无法注册

I am trying to register the nested generic type in DI container, but unable to register

抛出{开放的泛型服务类型需要注册开放的泛型实现类型。 （参数描述符）}错误

throws {Open generic service type requires registering an open generic implementation type. (Parameter descriptors)} error

实现的接口方法如下：

public class CustomerEvent<TEntity> : IEventConsumer<EntityInsertedEvent<TEntity>>,
    IEventConsumer<EntityUpdatedEvent<TEntity>>,
    IEventConsumer<EntityDeletedEvent<TEntity>> where TEntity : BaseEntity
{
    public void HandleEvent(EntityInsertedEvent<TEntity> eventMessage)
    {
        throw new NotImplementedException("Inserted");
    }

    public void HandleEvent(EntityUpdatedEvent<TEntity> eventMessage)
    {
        throw new NotImplementedException("Updated");
    }

    public void HandleEvent(EntityDeletedEvent<TEntity> eventMessage)
    {
        throw new NotImplementedException("Deleted");
    }
}

尝试

Assembly.GetExecutingAssembly()
    .GetTypes()
    .Where(item => item.GetInterfaces()
    .Where(i => i.IsGenericType)
        .Any(i => i.GetGenericTypeDefinition() == typeof(IEventConsumer<>))
            && !item.IsAbstract && !item.IsInterface)
    .ToList().ForEach(assignedTypes =>
    {
        assignedTypes.GetInterfaces()
            .Where(i => i.GetGenericTypeDefinition() == typeof(IEventConsumer<>)).ToList()
            .ForEach(imp =>
            {
                services.AddScoped(imp, assignedTypes);
            });
    });

但失败

推荐答案

没有简单的方法可以做到这一点。通常，您需要将开放通用的抽象映射到开放通用的实现，例如：

There is no easy way to do this. Typically, you need to map an open-generic abstraction to an open-generic implementation, like this:

services.AddTransient(typeof(IEventConsumer<>), typeof(CustomerEvent<>));

但是，这在您的情况下不起作用，因为MS.DI无法弄清楚该类的泛型类型参数如何 IEventCustomer< T> 应该映射到 CustomerEvent< TEntity> 的通用类型参数。例如，在解析 IEventCustomer< EntityInsertedEvent< Order>> 时，它将尝试创建 CustomerEvent< EntityInsertedEvent< Order>> ，尽管它应该已经创建了 CustomerEvent< Order> 。

This, however, will not work in your case because MS.DI is unable to figure out how the generic type argument for IEventCustomer<T> should maps to the generic type argument of CustomerEvent<TEntity>. When resolving an IEventCustomer<EntityInsertedEvent<Order>>, for instance, it will try to create a CustomerEvent<EntityInsertedEvent<Order>>, while it should have been creating a CustomerEvent<Order>.

这不是.NET的限制或CLR，但是它是MS.DI DI容器特有的限制，因为其他一些DI容器实际上能够进行此类映射。

This is not a limitation of .NET or the CLR, but a limitation that is specific to the MS.DI DI Container, because some other DI Containers are actually able to make these kinds of mappings.

不幸的是，使用MS.DI ，没有简单的出路。您唯一可以做的就是显式地进行所有可能的封闭通用注册，例如：

Unfortunately, with MS.DI, there is no easy way out. The only thing you can do is making all possible closed-generic registrations explicitly, e.g.:

s.AddTransient<IEventConsumer<EntityInsertedEvent<Order>>, CustomerEvent<Order>>();
s.AddTransient<IEventConsumer<EntityInsertedEvent<Customer>>, CustomerEvent<Customer>>();
s.AddTransient<IEventConsumer<EntityInsertedEvent<Product>>, CustomerEvent<Product>>();
s.AddTransient<IEventConsumer<EntityInsertedEvent<Employee>>, CustomerEvent<Employee>>();
s.AddTransient<IEventConsumer<EntityInsertedEvent<etc>>, CustomerEvent<etc>>();

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