ManualResetEvent的简单理解
看了很久的ManualResetEvent,但还是没看明白官方的解释,不妨让我们来看看定义的英文注释,或许更容易理解:
// Summary: // Initializes a new instance of the System.Threading.ManualResetEvent class // with a Boolean value indicating whether to set the initial state to signaled. // // Parameters: // initialState: // true to set the initial state signaled; false to set the initial state to // nonsignaled. [SecuritySafeCritical] public ManualResetEvent(bool initialState); // // Summary: // Sets the state of the event to nonsignaled, causing threads to block. // // Returns: // true if the operation succeeds; otherwise, false. [SecuritySafeCritical] public bool Reset(); // // Summary: // Blocks the current thread until the current System.Threading.WaitHandle receives // a signal, using a 32-bit signed integer to measure the time interval. // // Parameters: // millisecondsTimeout: // The number of milliseconds to wait, or System.Threading.Timeout.Infinite // (-1) to wait indefinitely. // // Returns: // true if the current instance receives a signal; otherwise, false. // // Exceptions: // System.ObjectDisposedException: // The current instance has already been disposed. // // System.ArgumentOutOfRangeException: // millisecondsTimeout is a negative number other than -1, which represents // an infinite time-out. // // System.Threading.AbandonedMutexException: // The wait completed because a thread exited without releasing a mutex. This // exception is not thrown on Windows 98 or Windows Millennium Edition. // // System.InvalidOperationException: // The current instance is a transparent proxy for a System.Threading.WaitHandle // in another application domain. public virtual bool WaitOne(int millisecondsTimeout); // // Summary: // Sets the state of the event to signaled, allowing one or more waiting threads // to proceed. // // Returns: // true if the operation succeeds; otherwise, false. [SecuritySafeCritical] public bool Set();
总结:
- ManualResetEvent 实例时接收一个Boolean类型的参数来初始化其状态,true表示畅通无阻的状态(signaled),线程不能阻塞,即使调用WaitOne也不能 阻塞;false表示是可阻塞的状态(nonsignaled),可以调用WaitOne等方法来阻塞的。这里初始化的只是一个状态。
- Reset方法把 ManualResetEvent 的状态设置为可阻塞的(nonsignaled),不管之前是什么状态,调用Reset都把状态设置为阻塞的(nonsignaled)。
- WaitOne 阻塞当前线程直到别的线程调用Set方法,只有ManualResetEvent 的状态是可阻塞(nonsignaled)时,WaitOne才能真正的起到作用;
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