c# - AutoResetEvent 何时重置？

Question

即使使用多年，我仍然不明白 AutoResetEvent 是如何工作的。

当谈到Set()时，是否应该有一部分代码在某处等待WaitOne()？

也就是说..如果在WaitOne()之前成功调用了Set()，那么在WaitOne()之前会自动Reset吗> 然后我会想念 Set 吗？

或者换句话说 - WaitOne() 是否使标志重置？

Answer 1

来自documentation :

The Set method releases a single thread. If there are no waiting threads, the wait handle remains signaled until a thread attempts to wait on it, or until its Reset method is called.

所以回答问题:

• 不必调用WaitOne，Reset 也会取消句柄信号。 (让一个类依赖于其他类的正确行为将是糟糕的设计。
• 在线程等待句柄或在 AutoResetEvent 上调用 Reset 之前，句柄保持信号状态。所以 Set 不会错过。当两个线程等待时，一个 Set 可能会丢失。查看文档:

There is no guarantee that every call to the Set method will release a thread. If two calls are too close together, so that the second call occurs before a thread has been released, only one thread is released - as if the second call did not happen. Also, if the Set method is called when there are no threads waiting and the AutoResetEvent is already signaled, the call has no effect.

• WaitOne 会取消向句柄发出信号，但并非每次等待都能保证做到这一点(请参阅前面的评论)

从你的问题中我得到的印象是它会帮助你更仔细地阅读文档，也许看看 the source code您将看到 .NET 类包装了 Windows Event 对象。参见 this article获取有关如何/可以使用 Event 对象的更多信息。