using System;

using System.Threading;

using System.Threading.Tasks;

​

public class Program

{

    public static void Main()

    {

        CancelParallelLoop();

    }

    static void CancelParallelLoop()

    {

        var cts = new CancellationTokenSource();

        cts.Token.ThrowIfCancellationRequested();

        cts.Token.Register(() => Console.WriteLine("** token cancelled"));

        // start a task that sends a cancel after 500 ms      

        cts.CancelAfter(500);

        try

        {

            ParallelLoopResult result =

                Parallel.For(0, 100,

                             new ParallelOptions()

                             {

                                 CancellationToken = cts.Token

                             },

                             x =>

                             {

                                 Console.WriteLine("loop {0} started", x);

                                 int sum = 0;

                                 for (int i = 0; i < 100; i++)

                                 {

                                     Thread.Sleep(2);

                                     sum += i;

                                 }

                                 Console.WriteLine("loop {0} finished", x);

                             });

        }

        catch (OperationCanceledException ex)

        {

            Console.WriteLine(ex.Message);

        }

    }

}