用取消令牌取消Task
CancellationTokenSource:取消令牌 cancellationTokenSource?.Cancel();：其中？表示判断cancellationTokenSource是否为null,如果不是null才取消，否则会造成找不到实例的异常- 当
!cancellationToken.IsCancellationRequested后则不再进入While循环中，最后等待Thread.Sleep(2000);后Task资源被释放。
internal class Class1
{private CancellationTokenSource cancellationTokenSource;public void CancelTask(){cancellationTokenSource?.Cancel();}public void process(){cancellationTokenSource = new CancellationTokenSource();CancellationToken cancellationToken = cancellationTokenSource.Token;Task.Run(() =>{while (!cancellationToken.IsCancellationRequested){Thread.Sleep(1000);}Thread.Sleep(2000);});}
}
