浅谈C#中取消令牌CancellationTokenSource

• 基础操作

              CancellationTokenSource cancellationTokenSource = new CancellationTokenSource();
              cancellationTokenSource.Token.Register(() =>
              {
                  Console.WriteLine("取消了1111");
              });
              cancellationTokenSource.Token.Register(() =>
              {
                  Console.WriteLine("取消了2222");
              });
              cancellationTokenSource.Cancel();

  取消了2222
  取消了1111

• 超时自动取消

1. new CancellationTokenSource(3000);

2. cancellationTokenSource.CancelAfter(3000);

• 关联取消

              CancellationTokenSource cancellationTokenSource = new CancellationTokenSource();
              CancellationTokenSource cancellationTokenSource2 = new CancellationTokenSource();
              cancellationTokenSource.Token.Register(() =>
              {
                  Console.WriteLine("取消了1111");
              });
              cancellationTokenSource2.Token.Register(() =>
              {
                  Console.WriteLine("取消了2222");
              });
              var linkedTokenSource = CancellationTokenSource.CreateLinkedTokenSource(cancellationTokenSource.Token,
                  cancellationTokenSource2.Token);
              linkedTokenSource.Token.Register(() =>
              {
                  Console.WriteLine("关联令牌被取消了");
              });
              //cancellationTokenSource.Cancel();
              cancellationTokenSource2.Cancel();

  关联令牌被取消了
  取消了2222

  令牌1和2的任意一个取消，关联令牌linkedTokenSource就会被取消。但是关联令牌linkedTokenSource取消，令牌1和2并不会取消。
• 判断取消

              CancellationTokenSource cancellationTokenSource = new CancellationTokenSource();
              cancellationTokenSource.Token.Register(() =>
              {
                  Console.WriteLine("取消了1111");
              });
              Task.Run(async () =>
              {
                  while (!cancellationTokenSource.IsCancellationRequested)
                  {
                      Console.WriteLine("一直在执行...");
                      await Task.Delay(1000);
                  }
              });
              cancellationTokenSource.CancelAfter(3000);

  一直在执行...
  一直在执行...
  一直在执行...
  取消了1111

              CancellationTokenSource cancellationTokenSource = new CancellationTokenSource();
              Task.Run(async () =>
              {
                  try
                  {
                      while (true)
                      {
                          //如果操作被取消则直接抛出异常
                          cancellationTokenSource.Token.ThrowIfCancellationRequested();
                          Console.WriteLine("一直在执行...");
                          await Task.Delay(1000);
                      }
                  }
                  catch (OperationCanceledException ex)
                  {
                      Console.WriteLine("取消了！");
                  }
              });
              cancellationTokenSource.CancelAfter(3000);

  一直在执行...
  一直在执行...
  一直在执行...
  取消了！

  使用ThrowIfCancellationRequested会抛出OperationCanceledException异常，需要自己捕获处理