Comments on: Synchronizing calls to the UI in a multi-threaded application

By: Groverboy

Groverboy — Wed, 23 Jan 2013 00:33:00 +0000

Very nice generalised design, thanks for sharing this. I’ve been using SynchronizationContext for some time and definitely find it preferable to using Control.BeginInvoke.

A minor criticism: cancellation does not look thread-safe. The worker thread reads class field stopRequested (QuoteService.Run) and the consumer thread writes to the field (QuoteService.Stop), but there is no thread synchronisation to prevent a race condition. This means the consumer may call Stop and begin writing to stopRequested when the worker thread reads the field (stopRequested still equals false), resulting in an additional iteration beyond the consumer request to cancel.

Thread synchronisation can be implemented by using either a lock statement or qualifying stopRequested by ‘volatile’.

So far as I know the race condition here has a minor consequence (potentially delayed cancel) unlike, for example, deposit to/withdrawal from a bank account. Can anyone think of a situation in which delayed cancel becomes a significant problem?

By: Mike

Mike — Mon, 24 Sep 2012 19:40:00 +0000

Million-dollar article! Thanks a million!

By: Freon

Freon — Sun, 23 Sep 2012 02:19:00 +0000

Fantastic little mechanism that solves the (thread)=>GUI problem nicely. Is scaleable and simple. WIN!

By: annamalai

annamalai — Fri, 08 Jul 2011 06:42:00 +0000

i fixed it by
changing syncContext.Post(OnQuoteChanged, args);
to
syncContext.Post(delegate
{
OnQuoteChanged(arg);
}, null);

By: annamalai

annamalai — Fri, 08 Jul 2011 04:48:00 +0000

i am getting error in this line
syncContext.Post(OnQuoteChanged, args); as follows
The best overloaded method match for ‘System.Threading.SynchronizationContext.Post(System.Threading.SendOrPostCallback, object)’ has some invalid arguments

Argument 1: cannot convert from ‘method group’ to ‘System.Threading.SendOrPostCallback’

the function signature is same as mentioned in the example.
please help is there any changes i need to make

By: Gabriel N. Schenker

Gabriel N. Schenker — Wed, 26 Jan 2011 21:39:14 +0000

@Eric: this is just a class inheriting from EventArgs and having two properties Symbol (string) and Quote (decimal) and a constructor which allows to set these properties.

By: Eric

Eric — Wed, 26 Jan 2011 20:38:23 +0000

Small beginner question: What is the QuoteEventArgs. I get this error: “type or namespace could not be found.” in this line public event EventHandler QuoteChanged;

If it’s a custom class could you provide an example one?

Thanks for the article it is very nice.

By: Mehdi

Mehdi — Sun, 20 Jun 2010 06:55:27 +0000

I learned a lot from this clear and easy DRY tutorial. This is exactly what i was looking for, Thank you very much.

By: ...

... — Thu, 12 Mar 2009 09:26:03 +0000

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By: ...

... — Tue, 03 Mar 2009 13:48:40 +0000

Gute Arbeit hier! Gute Inhalte.