using System;

using System.Threading;

using System.Threading.Tasks;

​

namespace ConsoleApp1

{

    public interface INotificationHandler<in TNotification>

        where TNotification : class

    {

        Task Handle(TNotification notification, CancellationToken cancellationToken);

    }

​

    public interface IRequestHandler<in TRequest, TResponse>

        where TRequest : class

    {

        Task<TResponse> Handle(TRequest request, CancellationToken cancellationToken);

    }

​

    class TestNotification

    {

        public int UserId { get; set; }

        public int Age { get; set; }

    }

​

    class TestRequest

    {

        public int UserId { get; set; }

    }

​

    class TestRequestHandler : IRequestHandler<TestRequest, int>

    {

        public Task<int> Handle(TestRequest request, CancellationToken cancellationToken)

        {

            return Task.FromResult(request.UserId);

        }

    }

​

    class TestNotificationHandler : INotificationHandler<TestNotification>

    {

        public Task Handle(TestNotification notification, CancellationToken cancellationToken)

        {

            Console.WriteLine("hello");

            return Task.CompletedTask;

        }

    }

​

    public class Program

    {

        public static void Main()

        {

            new TestNotificationHandler()

                        .Handle(new TestNotification(), CancellationToken.None);

​

            var result = new TestRequestHandler()

                                .Handle(new TestRequest() { UserId = 111 }, CancellationToken.None)

                                .Result;

​

            Console.WriteLine("result is " + result);

        }

    }

}

​