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Same project, different machines, one machine has cross threading issue

Answer 1

+2 A:

It's difficult to be certain without a little more information, but it sounds to me like the method that does the resizing can be called in more than one place. It's likely that your old Toshiba is a single-core machine, so the computer can't do more than one thing at once and the tab is resized by the main thread. On your newer Dell machine, which likely has multiple cores, a secondary thread is calling the method that does the resizing, and that's causing the exception to be thrown.

Look into the use of Control.InvokeRequired and Control.Invoke to handle synchronization between background threads and the UI thread.

Jim Mischel 2010-07-09 20:14:07

I agree with the first paragraph. However, don't use `Invoke`, and certainly don't use `InvokeRequired`. Use a `Task` or a `BackgroundWorker`.

Stephen Cleary 2010-07-09 20:26:18

If you want to update the UI from a thread other than the worker thread, you'll definitely need to use Invoke or something similar. A system timer event handler, for example, will have to use that. Does BackgroundWorker have an Invoke equivalent for updating the UI?

Jim Mischel 2010-07-09 20:51:43

Ok, this made total sense and I added a delegate to the timer method that is used to expand and contract the panel. When it is loading, I also locked the form creation method and initial panel adjustment and all the errors are now gone. These comments were very useful, thanks.

flavour404 2010-07-09 20:52:36

Ok, totally premature, nope still causing the same error. Took all the resize on load code out and set the control to its starting size, and put the label where I want it, but still erroring out when trying to display the form.

flavour404 2010-07-09 22:40:34

@flavour404: The error message means that the you have more than one thread running, and a non-UI thread is trying to update the form. You need to identify the thread (a timer, perhaps?) that's trying to access the UI. If you want to update the UI from a non-UI thread, you'll need to use Control.Invoke or something similar.

Jim Mischel 2010-07-12 16:11:23

I managed to work around the problem and stop the error. It was in fact a despatch timer, instantiated on form load that was causing the threading error. I since moved the despatch timer instantiation code to a button, so the first time the button is pressed the timer is created, and this has stopped the threading errors. Everything is working fine now, looks at the logs, no errors. All the answers were very helpful. Thanks.

flavour404 2010-07-13 22:51:13

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Same project, different machines, one machine has cross threading issue

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