Autofac, MediatR & multiple DLL projects

Question

I have several (eventually 100+) small DLL projects all based on MediatR. This means that the interfaces in use are just the IMediatR interfaces (IRequest<TResult>, IRequestHandler<IRequest<TResult>, TResult>). Since a lot of these do not have a UI and are called via orchestration from another DLL I was thinking I could create an Autofac Container project (DLL), register all the micro-services, then resolve what I need at runtime in another app that consumes my container. So far, so good.

Where I am running into problems is the registration of each and every CQRS handler. Right now, while everything is small in scope, they are being defined inline like this:

namespace My.Core.Container
{
    public class CoreDependencies
    {
        #region Properties
        public IMediator Mediator { get; private set; }
        public IContainer Container { get; private set; }

        private static ContainerBuilder _builder;
        #endregion

        #region Constructor
        public CoreDependencies()
        {
            _builder = new ContainerBuilder();

            // register MediatR types...
            _builder.RegisterSource(new ContravariantRegistrationSource());
            _builder.RegisterAssemblyTypes(typeof(IMediator).GetTypeInfo().Assembly).AsImplementedInterfaces();
            _builder.Register<SingleInstanceFactory>(ctx => 
            {
                var c = ctx.Resolve<IComponentContext>();
                return t => c.Resolve(t);
            });
            _builder.Register<MultiInstanceFactory>(ctx =>
            {
                var c = ctx.Resolve<IComponentContext>();
                return t => (IEnumerable<object>)c.Resolve(typeof(IEnumerable<>).MakeGenericType(t));
            });

            // ################################################## //
            // register EntityTree micro services...
            _builder.RegisterAssemblyTypes(typeof(My.Core.EntityTree.GetChildren).GetTypeInfo().Assembly).AsImplementedInterfaces();
            _builder.RegisterAssemblyTypes(typeof(My.Core.EntityTree.DeleteEntity).GetTypeInfo().Assembly).AsImplementedInterfaces();
            _builder.RegisterAssemblyTypes(typeof(My.Core.EntityTree.AddEntity).GetTypeInfo().Assembly).AsImplementedInterfaces();

            // register next micro services...
            // register next micro services...
            // ad naseum...
            // ################################################## //

            // Now build it...
            Container = _builder.Build();
            Mediator = Container.Resolve<IMediator>();
        }
        #endregion
    }
}

So, my question is: How do I correctly do this registration? Right now, 2 or 3 "cores" (micro-services) but next month, 20, next year, 200, etc...

TIA

Answer 1

Instead of manually register assembly by assembly, you could do Assembly Scanning to retrieve all assemblies you need, and then, register them in simple loop (code not tested):

var assemblies = /* get assemblies based on project type (web/desktop) */;
foreach(var assembly in assemblies)
{
    container.RegisterAssemblyTypes(assembly).AsImplementedInterfaces();
}

Btw, you should not expose your container as public property, unless you have very strong arguments to do so (service locator anti-pattern). Also SingleInstanceFactory and MultiInstanceFactory look pretty suspicious for me...