Autofac, MediatR & multiple DLL projects

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

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...