如何使用Autofac在构造函数中注入特定的实现

Question

我有两个类ILastActivityUpdator作为构造函数参数:UserService和AnonymousUserService.

public AnonymousUserService(ILastActivityUpdator lastActivityUpdator)
{
    if (lastActivityUpdator == null)
    {
        throw new ArgumentNullException("lastActivityUpdator");
    }
    this.lastActivityUpdator = lastActivityUpdator;
}

和上面类似UserService:

public UserService(ILastActivityUpdator lastActivityUpdator)
{
    if (lastActivityUpdator == null)
    {
        throw new ArgumentNullException("lastActivityUpdator");
    }
    this.lastActivityUpdator = lastActivityUpdator;
}

ILastActivityUpdator接口有一种方法:UpdateLastActivity(int userId).接口有两种实现,一种LastActivityUpdator叫做decorator AnonymousUserLastActivityUpdator,它继承LastActivityUpdator并向方法添加一些额外的功能,如下所示:

public class AnonymousUserLastActivityUpdator 
    : LastActivityUpdator, IAnonymousUserLastActivityUpdator
{
    public AnonymousUserLastActivityUpdator()
    { }

    public override void UpdateLastActivity(int userId)
    {
        base.UpdateLastActivity(userId);

        // Extra functionality
    }
}

我现在想用Autofac要连接的AnonymousUserService同AnonymousUserLastActivityUpdator和UserService同LastActivityUpdator.

我尝试的是为从基本接口派生的装饰器添加一个接口,如下所示:

public interface IAnonymousUserLastActivityUpdator : ILastActivityUpdator
{ }

然后我想我可以IAnonymousUserLastActivityUpdator在AnonymousUserService构造函数中使用它,一切都将正确自动装配.

不幸的是,它总是使用第一个实现,IAnonymousUserLastActivityUpdator因为它是早先注册的(字母顺序).

我怎样才能做到的是,AnonymousUserService得到AnonymousUserLastActivityUpdator注入和UserService的LastActivityUpdator？

Answer 1

Autofac有很好的文档记录,看起来你可以在这里找到你的内容.据我所知,如果您已经注册了更新程序

builder.RegisterType<LastActivityUpdator>();
builder.RegisterType<AnonymousUserLastActivityUpdator>();

那么你应该能够注册你的服务

builder.Register(c => new UserService(c.Resolve<LastActivityUpdator>()));
builder.Register(c => new AnonymousUserService(c.Resolve<AnonymousUserLastActivityUpdator>()));

要么

builder.RegisterType<UserService>().WithParameter(
    (p, c) => p.ParameterType == typeof(ILastActivityUpdator),
    (p, c) => c.Resolve<LastActivityUpdator>());

builder.RegisterType<AnonymousUserService>().WithParameter(
    (p, c) => p.ParameterType == typeof(ILastActivityUpdator),
    (p, c) => c.Resolve<AnonymousUserLastActivityUpdator>());

然后,当您解析容器UserService或AnonymousUserService从容器解析时,它们将获得正确的依赖关系.

顺便说一句,如果将接口注入到类中,那么该类应该与该接口(LSP)的所有实现一起正常运行.从类名称来看,它看起来AnonymousUserService只适用于AnonymousUserLastActivityUpdator而不是任何实现ILastActivityUpdator.如果是这种情况,那么IAnonymousUserLastActivityUpdator根据您的建议引入不同的抽象(如)可能是合适的.