How to cancel a Parallel.For or Parallel.ForEach loop

We can cancel the Parallel.For or Parallel.ForEach using a CancellationToken as shown below:

namespace CancelParallelLoops

{

    using System;

    using System.Linq;

    using System.Threading;

    using System.Threading.Tasks;

    class Program

    {

        public static void Main()

        {

            int[] nums = Enumerable.Range(0, 10000000).ToArray();

            CancellationTokenSource cts = new CancellationTokenSource();

           // Use ParallelOptions instance to store the CancellationToken

            ParallelOptions po = new ParallelOptions();

            po.CancellationToken = cts.Token;

            po.MaxDegreeOfParallelism = System.Environment.ProcessorCount;

            Console.WriteLine("Press any key to start. Press 'c' to cancel.");

            Console.ReadKey();            

            // Run a task so that we can cancel from another thread.

            Task.Factory.StartNew(() =>

            {

                if (Console.ReadKey().KeyChar == 'c')

                    cts.Cancel();

                Console.WriteLine("press any key to exit");

            });

            try

            {

                Parallel.ForEach(nums, po, (num) =>

                {

                    double d = Math.Sqrt(num);

                    Console.WriteLine("{0} on {1}", d, Thread.CurrentThread.ManagedThreadId);

                    po.CancellationToken.ThrowIfCancellationRequested();

                });

            }

            catch (OperationCanceledException e)

            {

                Console.WriteLine(e.Message);

            }

            Console.ReadKey();

        }

    }

}