using System;
using System.IO;
using System.Threading;

namespace Async08
{
    class Program
    {
        static void Main(string[] args)
        {
            var source = @"c:\dir\file.bin";
            var target = @"d:\dir\file.bin";
            using (var inStream = File.OpenRead(source))
            {
                using (var outStream = File.OpenWrite(target))
                {
                    using (var cts = new CancellationTokenSource())
                    {
                        var task = inStream.CopyToAsync(outStream, bufferSize: 4059, cancellationToken: cts.Token);
                        Console.WriteLine("Press 'c' to cancel.");
                        var key = Console.ReadKey().KeyChar;
                        if (key == 'c')
                        {
                            Console.WriteLine("Cancelling");
                            cts.Cancel();
                        }
                        Console.WriteLine("Wating...");
                        task.ContinueWith(t => { }).Wait();
                        Console.WriteLine("Status: {0}", task.Status);
                    }
                }
            }
        }
    }
}

    public static class CancellationTokenExtensions
    {
        public static async Task UntilCompletionOrCancellation(Task asyncOp, CancellationToken ct)
        {
            var tcs = new TaskCompletionSource<bool>();
            using (ct.Register(() => tcs.TrySetResult(true)))
            {
                await Task.WhenAny(asyncOp, tcs.Task);
            }
        }
    }

    public class CancellationTokenTest
    {
        public static void Run()
        {
            var cts = new CancellationTokenSource();
            Task.Run(async () => await test(), cts.Token);
            Console.ReadLine();
            cts.Cancel();
            Console.WriteLine("Cancel...");
            Console.ReadLine();
        }

        private static async Task test()
        {
            while (true)
            {
                await Task.Delay(1000);
                Console.WriteLine("Test...");
            }
        }
    }

Test...
Test...
Test...
 
Cancel...
Test...
Test...
Test...
Test...

public class CancellationTokenTest
    {
        public static void Run()
        {
            var cts = new CancellationTokenSource();
            Task.Run(async () => await test(cts.Token), cts.Token);
            Console.ReadLine();
            cts.Cancel();
            Console.WriteLine("Cancel...");
            Console.ReadLine();
        }

        private static async Task test(CancellationToken ct)
        {
            while (true)
            {
                await Task.Delay(1000, ct);
                Console.WriteLine("Test...");

                if (ct.IsCancellationRequested)
                {
                    break;
                }
            }
            Console.WriteLine("Test cancelled");
        }
    }

        private static async Task test2(CancellationToken ct)
        {
            bool isRunning = true;

            ct.Register(() =>
            {
                isRunning = false;
                Console.WriteLine("Query cancelled");
            });

            while (isRunning)
            {
                await Task.Delay(1000, ct);
                Console.WriteLine("Test...");
            }
            Console.WriteLine("Test cancelled");
        }