using System;

using System.Collections.Generic;

​

using System.Threading.Tasks;

public class Program

{

    static void Main(string[] args)

        {

            var service = new MyService();

            IList<TestClient> clients = new List<TestClient>();

            Console.WriteLine($"Start: {DateTime.Now:HH-mm-ss}");

            for (int i = 0; i < 5; i++)

            {

                //uncomment line A and comment line B to see different result

                service.Run(i);//line A

                //Task.Run(()=>service.Run(i)); //line B

            }

            Console.WriteLine($"Finish: {DateTime.Now:HH-mm-ss}");

            Console.ReadLine();

        }

    }

​

    public class TestClient

    {

​

    }

​

    public class MyService

    {

        public void Run(int i)

        {

            Task.Delay(3000).Wait();

            Console.WriteLine($"Processed {i} at {DateTime.Now:HH-mm-ss}");

        }

    }

}