Autofac命名注册构造函数注入 [英] Autofac named registration constructor injection

问题描述

Autofac是否支持在组件的构造函数中指定注册名称?

Does Autofac support specifying the registration name in the components' constructors?

例如:Ninject的NamedAttribute.

Example: Ninject's NamedAttribute.

推荐答案

您需要使用顶部的Autofac.Extras.Attributed包来实现此目的

You need to use the Autofac.Extras.Attributed package on top to achieve this

因此，假设您有一个接口和两个类:

So let's say you have one interface and two classes:

public interface IHello
{
    string SayHello();
}

public class EnglishHello : IHello
{
    public string SayHello()
    {
        return "Hello";
    }
}

public class FrenchHello : IHello
{
    public string SayHello()
    {
        return "Bonjour";
    }
}

然后您有一个消费者类，您要在其中选择要注入的实例:

Then you have a consumer class, which in you want to select which instance is injected:

public class HelloConsumer
{
    private readonly IHello helloService;

    public HelloConsumer([WithKey("EN")] IHello helloService)
    {
        if (helloService == null)
        {
            throw new ArgumentNullException("helloService");
        }
        this.helloService = helloService;
    }

    public string SayHello()
    {
        return this.helloService.SayHello();
    }
}

注册和解决:

ContainerBuilder cb = new ContainerBuilder();

cb.RegisterType<EnglishHello>().Keyed<IHello>("EN");
cb.RegisterType<FrenchHello>().Keyed<IHello>("FR");
cb.RegisterType<HelloConsumer>().WithAttributeFilter();
var container = cb.Build();

var consumer = container.Resolve<HelloConsumer>();
Console.WriteLine(consumer.SayHello());

注册此类使用方时不要忘记AttributeFilter，否则解析将失败.

Do not forget the AttributeFilter when you register such a consumer, otherwise resolve will fail.

另一种方法是使用lambda代替属性.

Another way is to use a lambda instead of attribute.

cb.Register<HelloConsumer>(ctx => new HelloConsumer(ctx.ResolveKeyed<IHello>("EN")));

我找到了第二种选择，因为您也避免在项目中引用autofac程序集(只是导入属性)，但这当然是个人观点.

I find the second option cleaner since you also avoid to reference autofac assemblies in your project (just to import an attribute), but that part is a personal opinion of course.

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