By default, Caliburn Micro uses the MEF. And, by default, the MEF uses attributes to identify components.

I’m pretty lazy and, given the choice, I’d rather use conventions and auto-registration. Luckily someone else was way ahead of me! And the MEFContrib project contains all the building blocks you need to create your own conventions.

I was originally planning on implementing a convention to register the first declared interface but, due to the vagaries of reflection, I took the easy way out and registered all interfaces from the same assembly (did I mention I’m lazy?).

    public class AppPartRegistry : PartRegistry
    {
        public AppPartRegistry()
        {
            this.Part().RegisterAllInterfaces();

            this.Scan(c => c.Assembly(typeof(AppPartRegistry).Assembly));
        }
    }

    public static class PartConventions
    {
        public static void RegisterAllInterfaces(this PartConventionBuilder<PartConvention> builder)
        {
            builder
                .ForTypesMatching(t => true)
                .ImportConstructor()
                .MakeNonShared()
                .Exports(e =>
                {
                    e.Export().Members(t => t.GetInterfaces().Where(i => i.Assembly == t.Assembly).ToArray());
                });
        }
    }

Update: Import (greediest) ctor, and make registrations transient.