Do I need to call Close() on a ManualResetEvent?

Question

I\'ve been reading up on .NET Threading and was working on some code that uses a ManualResetEvent. I have found lots of code samples on the internet. However, when reading

Answer 1

If you're using a ManualResetEvent with anonymous methods then it's obviously useful. But as Sam mentioned they can often be passed around into workers, and then set and closed.

So I would say it depends on the context of how you are using it - the MSDN WaitHandle.WaitAll() code sample has a good example of what I mean.

Here's an example based on the MSDN sample of how creating the WaitHandles with a using statement would exception:

System.ObjectDisposedException
"Safe handle has been closed"

const int threads = 25;

void ManualWaitHandle()
{
    ManualResetEvent[] manualEvents = new ManualResetEvent[threads];

    for (int i = 0; i < threads; i++)
    {
        using (ManualResetEvent manualResetEvent = new ManualResetEvent(false))
        {
            ThreadPool.QueueUserWorkItem(new WaitCallback(ManualWaitHandleThread), new FileState("filename", manualResetEvent));
            manualEvents[i] = manualResetEvent;
        }
    }

    WaitHandle.WaitAll(manualEvents);
}

void ManualWaitHandleThread(object state)
{
    FileState filestate = (FileState) state; 
    Thread.Sleep(100);
    filestate.ManualEvent.Set();
}

class FileState
{
    public string Filename { get;set; }
    public ManualResetEvent ManualEvent { get; set; }

    public FileState(string fileName, ManualResetEvent manualEvent)
    {
        Filename = fileName;
        ManualEvent = manualEvent;
    }
}