问题
If I am using EventWaitHandle (or AutoResetEvent, ManualResetEvent) to synchronise between threads then do I need to call the Close() or Dispose() methods on that event handle when I am done with it?
EventWaitHandle inherits from WaitHandle, which implements IDisposable. And FxCop complains if I don't implement IDisposable on any class that contains an EventWaitHandle. So this suggests that I do need to call it.
However none of these MSDN usage examples call Dispose() or Close():
http://msdn.microsoft.com/en-us/library/system.threading.eventwaithandle(VS.80).aspx http://msdn.microsoft.com/en-us/library/system.threading.manualresetevent(VS.80).aspx http://msdn.microsoft.com/en-us/library/system.threading.autoresetevent(VS.80).aspx
Is this just an example of Microsoft ignoring their own advice?
回答1:
The disposable resource of an EventWaitHandle is actually a SafeHandle (wrapped in a SafeWaitHandle). SafeHandle implements a finalizer, which eventually makes sure the necessary resource is release, so it should be safe to let the garbage collector / finalizer thread handle it in this case.
However, it is always a good idea to explicitly call Dispose() when the resource is no longer needed.
The threading chapter in C# 3.0 in a Nutshell states
This practice is (arguably) acceptable with wait handles because they have a light OS burden (asynchronous delegates rely on exactly this mechanism to release their
IAsyncResult's wait handle).
回答2:
You need to dispose them explicitly. Close() is more appropriate for them as it does call Dispose().
回答3:
Class definitions from MSDN:
public class EventWaitHandle : WaitHandle
public abstract class WaitHandle : MarshalByRefObject, IDisposable
So yes you must as WaitHandle is IDisposable. FxCop would find this as a rule violation if you didn't.
来源：https://stackoverflow.com/questions/659840/do-i-need-to-dispose-or-close-an-eventwaithandle