System.Net.LazyAsyncResult.LazilyCreateEvent C# (CSharp) Method

        private bool LazilyCreateEvent(out ManualResetEvent waitHandle)
        {
            waitHandle = new ManualResetEvent(false);
            try
            {
                if (Interlocked.CompareExchange(ref _event, waitHandle, null) == null)
                {
                    if (InternalPeekCompleted)
                    {
                        waitHandle.Set();
                    }
                    return true;
                }
                else
                {
                    waitHandle.Dispose();
                    waitHandle = (ManualResetEvent)_event;

                    // There's a chance here that _event became null.  But the only way is if another thread completed
                    // in InternalWaitForCompletion and disposed it.  If we're in InternalWaitForCompletion, we now know
                    // IsCompleted is set, so we can avoid the wait when waitHandle comes back null.  AsyncWaitHandle
                    // will try again in this case.
                    return false;
                }
            }
            catch
            {
                // This should be very rare, but doing this will reduce the chance of deadlock.
                _event = null;
                if (waitHandle != null)
                {
                    waitHandle.Dispose();
                }

                throw;
            }
        }