using System;

using System.Threading;

public class Program

{

    public static void Main()

    {

        var task = new Action<object, CancellationToken>((state, token) => {

            for(var i = 0; i < 10; i++){

                if(token.IsCancellationRequested)

                {

                    //throw new NotImplementedException();

                    Console.WriteLine("Break task.");

                    return;

                }

                Thread.Sleep(10);

            }

            Console.WriteLine("Task has been completed.");

        });

        var cts = new CancellationTokenSource();

        cts.Token.Register(() => {

            //throw new NotImplementedException();

            Console.WriteLine("Cancelled.");

        });

        var t = ThreadPool.QueueUserWorkItem(state => { task(state, cts.Token); });

        cts.Cancel(false);

        Console.WriteLine("Hello World.");

        Thread.Sleep(500);

    }

}