System.Threading.Monitor question

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From: Jon Shemitz (jon_at_midnightbeach.com)
Date: 02/16/04 

Date: Mon, 16 Feb 2004 12:55:48 -0800

Exploring the C# lock, I wrote the simple multi-threaded IEnumerator
consumer, below. It simply reads elements and adds them to List, a
private ArrayList member of the same object as threadProc().

I originally wrote this without the Thread.Sleep(0); line, and I found
that - no matter how big the list or how many threads - one thread
would consume the whole list. Adding the Thread.Sleep(0); line let the
threads share the list as expected.

>From this I conclude

> lock() (System.Threading.Monitor.Enter()) will not block
> if another thread is waiting on the same object;
> only if another thread already has it locked.

Correct?

  private void threadProc()
  {
    object Current;
    do
    {
      lock (Enumerator)
        Current = Enumerator.MoveNext()
          ? Enumerator.Current
          : null;
      if (Current != null)
        List.Add(Current);
      Thread.Sleep(0);
    } while (Current != null);
  } 

-- 
programmer, author  http://www.midnightbeach.com
and father          http://www.midnightbeach.com/hs

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