协作式取消 CancellationTokenSource

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Threading;
namespace TaskApp
{
class Program
{
static void Main(string[] args)
{
//CancellationTokenSource:IDispose
using (CancellationTokenSource cts = new CancellationTokenSource())
{

ThreadPool.QueueUserWorkItem(o => Caculate(cts.Token, 60));

Console.ReadKey();
//lanch cancel method
cts.Cancel();

Console.ReadKey();
}
}

/// <summary>
/// Caculate
/// </summary>
/// <param name="ct">CancellationToken</param>
/// <param name="maxNumber"></param>
private static void Caculate(CancellationToken ct,int maxNumber)
{
int sum = 0;
for (int i = 0; i < maxNumber; i++)
{
if (!ct.IsCancellationRequested)
{
Thread.Sleep(1000);
sum += i;
}
else
{
Console.WriteLine("Caculate is cancelled:sum={0}", sum);

return;
}

}
Console.WriteLine("Caculate Finished:{0}!",sum);
}
}
}

CancellationToken 中肯定存在一种传入方法后能实时刷新的机制，CancellationTokenSource 的实例调用 Cancel方法后 ，Caculate 方法能感知到这种变化。