Library tutorials & articles
.NET Threading Part I
- Introduction
- Creating Threads
- Thread Pools
- Synchronization Objects
- Race Condition
- Join
- AutoResetEvent & Timer
Synchronization Objects
The previous code contains some rather inefficient coding when the main thread
cleans up. I repeatedly test the queue length every second until the queue length
reaches zero. This may mean that the process will continue executing for up
to a full second after the queues are finally drained. Wow! I can't have that.
OK! Maybe that's not a good reason to change the code, but it is a convenient
excuse for me to introduce you to the System.Threading.ManualResetEvent
class. Using a ManualResetEvent object, I could trigger
the main thread to complete as soon as the last ware was consumed. I'll do this
by creating two new instance data members, a bool WaitForComplete
to tell us when the main thread is waiting to exit and a ManualResetEvent
Event object that will signal the main thread to exit.
public void Wait()
{
if (QueueLength == 0)
{
return;
}
Event = new ManualResetEvent(false);
WaitForComplete = true;
Event.WaitOne();
}
public void Consume(Object obj)
{
Console.WriteLine("Thread {0} consumes {1}",
Thread.CurrentThread.GetHashCode(), //{0}
((Ware) obj).id); //{1}
Thread.Sleep(100);
QueueLength--;
if (WaitForComplete)
{
if (QueueLength == 0)
{
Event.Set();
}
};
}
When the consuming thread finishes consuming a ware and detects that the WaitForComplete
is true, it will trigger the Event when the queue length is zero. Instead of
calling the while block when it wants to exit, the main thread calls the Wait
instance method. This method sets the WaitForComplete flag and
waits on the Event object.
Randy's article are Copyright 1998-2003 Randy Charles Morin
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I was asked to do the following:
write the method call to begin running the thread and begin processing
(a) namespace = testProject
(b) form to run = frmMain
All the things that I have read on threading so far say that a thread point to a function of whatever comes after the "addressOf" in the argument. Therefore, I don't understand what (a) and (b) are trying to refer to or specify. If you happen to understand what that question is looking for, or know any good literature I can look at for the given topic, please let me know. Thank you.
email me
Are you ensuring that the page doesn't finish loading before both threads have returned a result? Otherwise, you may find that ASP.NET is outputting the page to the client before the thread has actually called the callback!
Yes...and if I may add, rather hesitantly at this juncture, I did think about that.
What surprised me however was when I ran this in debugging mode, I as able to trace both callbacks
and in one case the dataset returned had no data. I wonder if there are any issues with returning non-simple types
in the event driven call back. May be, using the delegate mechanism may work. I havn't done
much callback based threading so far...
This thread is for discussions of .NET Threading Part I.