using System;

using System.Threading;

using System.Threading.Tasks;

using Microsoft.Extensions.DependencyInjection;

using Microsoft.Extensions.Hosting;

​

namespace ConsoleApp3 {

​

    class Program {

        class MyService : BackgroundService {

            readonly string _name;

​

            public MyService(string name) => _name = name;

            protected override Task ExecuteAsync(CancellationToken stoppingToken) {

                Console.WriteLine("Execute {0}", _name);

                return Task.CompletedTask;

            }

        }

​

        static void Main() {

            var host1 = Host.CreateDefaultBuilder()

                .ConfigureServices((context, services) => {

                    services.AddSingleton<IHostedService>(new MyService("host1-1"));

                    services.AddSingleton<IHostedService>(new MyService("host1-2"));

                })

                .Build();

​

            var host2 = Host.CreateDefaultBuilder()

                .ConfigureServices((context, services) => {

                    services.AddHostedService(f => new MyService("host2-1"));

                    services.AddHostedService(f => new MyService("host2-2"));

                })

                .Build();

​

            Task.WhenAll(host1.RunAsync(), host2.RunAsync());

        }

    }

​

}

​