Can MessageBox.Show cause cross-thread exceptions?

Question

Can I call MessageBox.Show on a child thread without worrying about a cross-thread exception? I know the ostensible answer would be "try it and find out", which I did, successfully, but I've noticed that Windows 7 seems to be less strict about raising cross-thread exceptions than Windows XP.

So, is it documented anywhere that this would be safe to do from a child thread?

Answer 1

If you call MessageBox.Show("text") without an owner window you are save. If you call MessageBox.Show like MessageBox.Show(this,"text") specifying the owner window things are different.

I have seen that in Windows XP you are save but in Windows 7 you will run into a cross-thread exception if the owner window is running in a different thread than the thread from which you call the MessageBox!

Answer 2

No, it will not cause any "cross-thread" exceptions. That's because the MessageBox is not a member of a class running on the UI thread.