using System;

using System.Diagnostics;

using System.Threading;

using System.Threading.Tasks;

​

public class Program

{

    public static async Task Main()

    {               

        Stopwatch stopWatch = new Stopwatch();

        stopWatch.Start();

        Parallel.Invoke(

            () => SleepTask(1),

            () => SleepTask(2),

            () => SleepTask(3),

            () => SleepTask(4)

        );

        stopWatch.Stop();

        Console.WriteLine("");  

        Console.WriteLine($"Total Time: Parallel: {stopWatch.ElapsedMilliseconds}ms");  

        Console.WriteLine("");  

        stopWatch.Reset();

        stopWatch.Start();

        SleepTask(1);       

        SleepTask(2);   

        SleepTask(3);   

        SleepTask(4);   

        stopWatch.Stop();

        Console.WriteLine("");  

        Console.WriteLine($"Total Time: Sequential: {stopWatch.ElapsedMilliseconds}ms");    

        Console.WriteLine("");  

        stopWatch.Reset();

        stopWatch.Start();

        for (int i = 1 ; i <= 5 ; i++ )  {

            await Task.Run(() =>  {

                SleepTask(i);

            });

        };

        stopWatch.Stop();

        Console.WriteLine("");  

        Console.WriteLine($"Total Time: Awaited: {stopWatch.ElapsedMilliseconds}ms");   

        Console.WriteLine("");  

    }   

    static void SleepTask(int number)

    {

        Console.WriteLine($"SleepTask {number} started Thread {Thread.CurrentThread.ManagedThreadId}");     

        Thread.Sleep(750);      

        Console.WriteLine($"SleepTask {number} completed Thread {Thread.CurrentThread.ManagedThreadId}");

    }

}