Register MediatR handlers in Asp.Net 5 / vNext / Core

MediatRExtensions.cs

namespace Microsoft.AspNet.Builder
{
    public static class MediatRExtensions
    {
        public static IServiceCollection AddMediatR(this IServiceCollection services, params Assembly[] handlerAssemblies)
        {
            services.AddTransient<IMediator>(x => new Mediator(x.GetService<SingleInstanceFactory>(), x.GetService<MultiInstanceFactory>()));
            services.AddTransient<SingleInstanceFactory>(x => t => x.GetRequiredService(t));
            services.AddTransient<MultiInstanceFactory>(x => t => x.GetServices(t));

            foreach (var assembly in handlerAssemblies)
            {
                foreach (var type in assembly.ExportedTypes.Select(t => t.GetTypeInfo()).Where(t => t.IsClass && !t.IsAbstract))
                {
                    var interfaces = type.ImplementedInterfaces.Select(i => i.GetTypeInfo()).ToArray();

                    foreach (var handlerType in interfaces.Where(i => i.IsGenericType && i.GetGenericTypeDefinition() == typeof(IAsyncRequestHandler<,>)))
                    {
                        services.AddTransient(handlerType.AsType(), type.AsType());
                    }

                    foreach (var handlerType in interfaces.Where(i => i.IsGenericType && i.GetGenericTypeDefinition() == typeof(INotificationHandler<>)))
                    {
                        services.AddTransient(handlerType.AsType(), type.AsType());
                    }

                    foreach (var handlerType in interfaces.Where(i => i.IsGenericType && i.GetGenericTypeDefinition() == typeof(IRequestHandler<,>)))
                    {
                        services.AddTransient(handlerType.AsType(), type.AsType());
                    }
                }
            }

            return services;
        }
    }
}