Question

If I m looping through a prolonged operation (say, processing files) and I want to update a progress bar, I need to use DoEvents, from what I can understand.

But calling it during every loop of the function only results in the progress bar s animation being played back really fast (or slow, depending on the operation). I understand that this is because DoEvents allows the progress bar to "breathe", for lack of a better word, causing it and the rest of the form to refresh.

My question is, how do you know that it s appropriate to call DoEvents? Obviously you can t just call it on a whim however-often you feel like it - this results in sporadic animations, among other things. So is there some quick method to check if a form/application needs a DoEvents called?

Answer 1

Oh, duh - I just smacked myself.

I should just use a background thread to process, and leave the UI thread alone.

Answer 2

Instead of messing around with threads, you can use a BackgroundWorker. It simplifies performing work and updating controls on a Form as you cannot update a UI Control directly from a non-UI thread. The example in the docs updates a Label control, but you can easily modify it to use a ProgressBar.

Answer 3

If you don t want to fiddle around with threads and you don t mind a little beta-testing, the Visual Studio Async CTP might be worth a look -- it s basically "DoEvents done the right way" (and more).

For an introduction to these new async features, I recommend to check out Eric Lippert s blog.

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