IServiceCollectionExtensions.cs

public static class IServiceCollectionExtensions
{
	public static IServiceCollection ConnectImplementations<TService>(this IServiceCollection services, Assembly assembly)where TService : class
	{
		return services.ConnectImplementations(typeof (TService), assembly);
	}

	public static IServiceCollection ConnectImplementations(this IServiceCollection services, Type serviceType, Assembly assembly)
	{
		if (!serviceType.IsInterface) throw new ArgumentException($"{nameof(serviceType)} must be an interface");
        
		var concreteTypes = assembly.ExportedTypes.Select(t => t.GetTypeInfo()).Where(ti => ti.IsClass && !ti.IsAbstract);
        
		foreach (var type in concreteTypes)
		{
			var interfaces = type.ImplementedInterfaces.Select(i => i.GetTypeInfo()).ToArray();
            
			foreach (var @interface in interfaces.Where(i => i.IsGenericType && i.GetGenericTypeDefinition() == serviceType))
			{
				services.AddTransient(@interface.AsType(), type.AsType());
			}

			foreach (var @interface in interfaces.Where(i => !i.IsGenericType && i.IsAssignableFrom(serviceType)))
			{
				services.AddTransient(@interface.AsType(), type.AsType());
			}
		}

		return services;
	}
}