Autofac: Resolve all instances of a Type

Question

Given the following registrations

builder.Register<A>().As<I>();
builder.Register<B>().As<I>();
builder.Register<C>().As<I>();

var container = builder.Build();

I am looking to resolve all instances of type I as a IEnumerable (Array or Collection it doesnt matter).

In Windsor I would have written the following.

foreach(I i in container.ResolveAll<I>())
{
 ...
}

I am migrating from Windsor to Autofac 1.4.4.561 but can't see the equivalent syntax.

Thanks.

Answer 1

Warning: may be from pre 1.4, but should still be the right direction...

Two ways:

1) Use the collection registration

var builder = new ContainerBuilder();
builder.RegisterCollection<ILogger>()
  .As<IEnumerable<ILogger>>();

builder.Register<ConsoleLogger>()
  .As<ILogger>()
  .MemberOf<IEnumerable<ILogger>>();

builder.Register<EmailLogger>()
  .As<ILogger>()
  .MemberOf<IEnumerable<ILogger>>();

Then:

var loggers = container.Resolve<IEnumerable<ILogger>>();

which gives you an IEnumerable.

or 2) You can use the ImplicitCollectionSupport module, which will make your code above work as listed - just add the registerModule call...

builder.RegisterModule(new ImplicitCollectionSupportModule());
builder.Register(component1).As<ILogger>;
builder.Register(component2).As<ILogger>;

Then resolve a collection of ILogger rather than looking for resolving all.

var loggers = container.Resolve<IEnumerable<ILogger>>();

which gives you an IEnumerable, again.

Answer 2

An update for the sake of the new (2.x) version. All you need now is:

container.Resolve<IEnumerable<I>>();

There's no longer a need for RegisterCollection() or ImplicitCollectionSupportModule - this functionality comes out of the box.