Medusa.net/Medusa.Core/Extensions/ApplicationBuilderExtensions.cs

using Medusa.Core.Handlers;
using Medusa.Core.Services;
using System.Reflection;

namespace Medusa.Core.Extensions
{
    public static class ApplicationBuilderExtensions
    {
        public static IApplicationBuilder UseHandlers(this IApplicationBuilder app)
        {
            var handlerService = app.ApplicationServices.GetRequiredService<IHandlerService>();

            var assembly = Assembly.GetEntryAssembly() ?? throw new InvalidOperationException("Could not find entry assembly.");
            var types = assembly.GetTypes().Where(t => t.GetInterfaces().Contains(typeof(IHandler)) || 
            (t.IsSubclassOf(typeof(Handler)) && !t.IsAbstract));

            handlerService.Handlers.AddRange(types);

            return app;
        }
    }
}