The best way to register your Autofac service is to use the convention approach. However there are always exceptions to the rule, and sometimes the registration process needs to be done on a case by case basis. When this happens, we usually end up with something like this in the Autofac module or the container builder:
builder.RegisterType<Foo>().As<IFoo>().SingleInstance();
builder.RegisterType<Bar>().AsSelf().AsImplementedInterfaces().InstancePerLifetimeScope();
builder.RegisterType<Baz>().AsImplementedInterfaces().Named("Baz").InstancePerDependency();
This can get unweildly quickly. The other problem is that when modifying a serice, it is not clear what it's lifestyle is.
The Autofac.AttributeRegistration library helps to clean up the registrations by moving the registration adjacent to the class declaration but using attributes.
To register a class, add the appropriate attribute:
[SingleInstance]
public class Foo : IFoo { }
And then in your container builder or module, call RegisterByAttributes(params Assembly[]):
builder.RegisterByAttributes(ThisAssembly, typeof(OtherAssemblyType).Assembly)
For other lifestyles, you can use the [InstancePerDependency], [InstancePerLifetimeScope] and [InstancePerHttpRequest] attributes.
By default, all types are registered as AsSelf() and as AsImplementedInterfaces().
To prevent the registration as AsImplementedInterfaces(), set the AsImplementedInterface attribute property to false, eg [SingleInstance(AsImplementedInterface = false)]. If the type does not have any interfaces, this option is not required.
To register a type as a named service, use the Name attribute property, eg [SingleInstance(Name = "Test")].
If you want to register the type as AutoActive, use the AutoActive attribute property, eg [SingleInstance(AutoActive = true)]
If you need to register a type in several different ways, you can specify the attribute more than once:
[SingleInstance(AsImplementedInterface = false)]
[SingleInstance(Name = "Test", AsImplementedInterface = false)]
public class MultiRegistrationClass
The registration is run for each attribute, so in this case the type is registered twice.
Autofac.AttributeRegistration is a Portable Class Library and has been tested against Autofac 3.1.5 and the following library types:
- .NET 4.5
- .NET 4 Client Profile
- .NET 4
- Sliverlight 5
- Windows Store
- Windows Phone 8
If you are having problems compiling with errors referring to System.Core 2.0.5.0, see here.
If you are trying to use Autofac in a VSTO application, you may get build errors. This is related again to System.Core (Portable class library). The solution is not to reference and PCL assemblies from the VSTO project directly.