By using this site, you agree to our updated Privacy Policy and our Terms of Use. Manage your Cookies Settings.
459,292 Members | 1,642 Online
Bytes IT Community
+ Ask a Question
Need help? Post your question and get tips & solutions from a community of 459,292 IT Pros & Developers. It's quick & easy.

"Cross-thread operation not valid" even when .InvokeRequired is false

P: n/a
I'm getting a "Cross-thread operation not valid" Exception and I can't
figure out why.

I've got a BackgroundWorker that creates a UserControl with a whole lot
of other user controls inside of it, full of data I'm getting from the
database. When my background worker completes I take e.Result and cast
it back into a UserControl. I create a TabPage, add the returned
UserControl to the Controls of the new TabPage and *BAM* there's my
exception.

Just before I add the UserControl to the new TabPage's Controls I've
looked at the InvokeRequired properties for the UserControl, the new
TabPage and even my main form and they're all false, leading me to
believe that I should't expect to see such a cross-thread operation.

What gives?

Jan 19 '06 #1
Share this Question
Share on Google+
1 Reply


P: n/a
Mesan <93*****@gmail.com> wrote:
I'm getting a "Cross-thread operation not valid" Exception and I can't
figure out why.

I've got a BackgroundWorker that creates a UserControl with a whole lot
of other user controls inside of it, full of data I'm getting from the
database. When my background worker completes I take e.Result and cast
it back into a UserControl. I create a TabPage, add the returned
UserControl to the Controls of the new TabPage and *BAM* there's my
exception.

Just before I add the UserControl to the new TabPage's Controls I've
looked at the InvokeRequired properties for the UserControl, the new
TabPage and even my main form and they're all false, leading me to
believe that I should't expect to see such a cross-thread operation.

What gives?


Well, you should never have a control in a Window which "belongs" to a
different thread. The control itself "belongs" to the worker thread -
and although it sounds like InvokeRequired called on the UserControl
should really return true, even if you used Invoke you wouldn't solve
the problem as you'd then be in the wrong thread from the form's point
of view.

My *guess* is that the reason InvokeRequired isn't spotting the problem
is that the worker thread isn't running a message pump - but that's
only a guess.

Just create all the controls on your main UI thread, doing the heavy
non-UI-related work on another thread, and you should be fine.

--
Jon Skeet - <sk***@pobox.com>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
If replying to the group, please do not mail me too
Jan 19 '06 #2

This discussion thread is closed

Replies have been disabled for this discussion.