Autofac register all of type IFoo named IFoo.Name

Question

Just learning Autofac and struggling to rgister a handful of named instances by convention.

public interface IFoo
{
    string AutoFactName{ get; }
    object DoSomething();
}

looking at this interface what i am trying to accomplish is something along these lines

        builder.RegisterTypes()
            .AssignableTo<IFoo>()
            .As<IFoo>()
            .Named<IFoo>(i => i.AutoFactName);

I have tried a few variations of something to this effect. the end goal is to dynamically register and resolve instances.

Answer 1

You should not need instances to register your types in Autofac. If you need information from your type it is better to use meta information like Attribute. Something like that :

[FooMetadata("Foo1")]
public class Foo1 : IFoo 
{ }

and then use this metadata while registering

builder.RegisterAssemblyTypes(assembly)
        .AssignableTo<IFoo>()
        .Named<IFoo>(t => t.GetCustomAttribute<FooMetadata>().Foo);

If you rely need to get the named type in your instance you can do it with a IRegistrationSource

public class NamedFooRegistrationSource : IRegistrationSource
{
    public bool IsAdapterForIndividualComponents => false;

    public IEnumerable<IComponentRegistration> RegistrationsFor(
        Service service,
        Func<Service, IEnumerable<IComponentRegistration>> registrationAccessor)
    {

        KeyedService keyedService = service as KeyedService;

        if (keyedService == null || keyedService.ServiceKey.GetType() != typeof(String))
        {
            yield break;
        }

        IComponentRegistration registration = RegistrationBuilder
            .ForDelegate(keyedService.ServiceType, (c, p) =>
            {
                Type foosType = typeof(IEnumerable<>).MakeGenericType(keyedService.ServiceType);
                IEnumerable<IFoo> foos = (IEnumerable<IFoo>)c.Resolve(foosType);

                foos = foos.Where(f => f.AutoFactName == (String)keyedService.ServiceKey).ToArray();
                if (foos.Count() == 0)
                {
                    throw new Exception($"no Foo available for {keyedService.ServiceKey}");
                }
                else if (foos.Count() > 1)
                {
                    throw new Exception($"more than 1 Foo available for {keyedService.ServiceKey}");
                }
                else
                {
                    return foos.First();
                }
            })
            .Named((String)keyedService.ServiceKey, keyedService.ServiceType)
            .CreateRegistration();

        yield return registration;
    }
}

and then register your Foo this way :

builder.RegisterAssemblyTypes(assembly)
        .AssignableTo<IFoo>()
        .As<IFoo>();
builder.RegisterSource<NamedFooRegistrationSource>();