using System;

using System.Linq;

using System.Collections.Generic;

using System.Threading;

using System.Threading.Tasks;

​

public class Program

{

    private static IList<int> items = Enumerable.Range(1, 80).ToArray();

    private static int _millisecondsDelay = 500;

    private const int MaxOfParall = 5;

    private static int cont = 0;

    private static int contFor = 1;

    public static async Task Main()

    {

        //  runs a normal foreach loop going through the IList<int> items

        //  and waiting the required _millisecondsDelay on each item

        // await RunNormalForEach(); //TimeOut

        Console.WriteLine("");

​

        //  runs a Parallel.ForEach loop going through the IList<int> items

        //  and waiting the required _millisecondsDelay on each item

        await RunParallelForEach();

        Console.WriteLine("***Total cont="+cont);

    }

    private static async Task RunParallelForEach()

    {

        var timerParallel = System.Diagnostics.Stopwatch.StartNew();

        var options = new ParallelOptions() { MaxDegreeOfParallelism = MaxOfParall };

        Parallel.ForEach(items, options,  item => 

        {

            System.Threading.Thread.Sleep(_millisecondsDelay);

             LogItemAndThread(item);

            Console.WriteLine("");

            Console.WriteLine("Next Parallel.ForEach"+contFor++);

            //cont = 0;

        });

        timerParallel.Stop();

        Console.WriteLine("");

        Console.WriteLine("Parallel.ForEach Elapsed (s): "+timerParallel.Elapsed.TotalSeconds);

        Console.WriteLine("");

    }

    private static async Task LogItemAndThread(int item)

    {

        await Task.Run(() => {

            //System.Threading.Thread.Sleep(_millisecondsDelay);

            var threadId = Thread.CurrentThread.ManagedThreadId.ToString().PadRight(4, ' ');

            Console.WriteLine(cont+".-ManagedThreadId "+threadId+": "+item);

            cont++;

        });

    }

​

    private static async Task RunNormalForEach()

    {

        var timerNormal = System.Diagnostics.Stopwatch.StartNew();

        //await Task.Run(async() =>{

            foreach (var item in items)

            {

                System.Threading.Thread.Sleep(_millisecondsDelay);

                await LogItemAndThread(item);

                Console.WriteLine("Next Normal foreach:");

            }

        //}); 

        timerNormal.Stop();

        Console.WriteLine("");

        Console.WriteLine("foreach Elapsed (s): {timerNormal.Elapsed.TotalSeconds:N2}");

        Console.WriteLine("");

    }

}