An extra click required to get out of a while loop using .DoEvents() ?

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Hi folks, I wrote a small API gui to communicate over foundation fieldbus.

I've used a While loop that constantly reads some parameter values from the bus.
At the end of the While loop, I put

VB

Application.DoEvents()

so that I can use another button to stop the reading process. It all seems good and easy.. but there's one problem: when I get the While loop running and wish to stop the process, I have to first click somewhere on the form, anywhere, before I could click any buttons(either 'stop reading' or 'reset' button mostly). That extra click makes my form seem unresponsive and lame.

I wonder whether this is a problem pertaining to DoEvents() or my use of Foundation fieldbus.

Anyone experience this 'extra click' before??

Posted 15-Mar-12 11:50am

SandiegoSSD

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Sergey Alexandrovich Kryukov · Answer 1 · 2012-03-15T12:56:00

Yes, and not just this. Never use DoEvents for such purposes. Always use a separate thread for anything which has it's own linear or circular logic, and for anything which contains blocking calls or contain lengthy operation. Even though DoEvents can work as a quick and dirty UI thread based work-around, it's not so quick but is too dirty for many cases to work correctly.

If you use a non-UI thread with UI applications, you need to understand that you cannot call any UI methods or properties directly from such thread, you need to use invocation mechanism I describe in detail in my past answers. Please see:
Control.Invoke() vs. Control.BeginInvoke()[^],
Problem with Treeview Scanner And MD5[^].

Please also see more references on threading based on my past answers:
How to get a keydown event to operate on a different thread in vb.net[^],
Control events not firing after enable disable + multithreading[^].

—SA