Need help with multithreading and InvalidOperatio nException

[Ian Toltz]

I've got a form element (a wizard, actually) which is giving me
problems when I try to invoke some of its methods from one of the
methods of a filesystemwatch er. Basically the watcher sits there
waiting to see the file and then it's supposed to go to the next page
(wizard1.Next() ).

I get an InvalidOperatio nException when I do this, though, and as near
as I can tell it's because the watcher creates a new thread and it's
trying to access the form object from a different thread. I don't know
how to fix this, though. Any ideas? I found this helpful page (http://
msdn2.microsoft .com/en-us/library/ms171728.aspx) which seems to be
exactly what I'm asking about, but I just can't figure it out. I've
tried to adapt it to my situation, but it's just over my head... In
particular, the whole backgroundwatch er thing isn't working. For
example, if I do "BackgroundWatc her bgw" and then on the very next
line something like "bgw=new BackgroundWatch er()" it tells me that the
variable bgw is unknown.

Is there any way to force a FileSystemWatch er to use the same thread
it's started in? I don't want or need the user to do anything until
it's done looking anyways.

[Jon Skeet [C# MVP]]

Ian Toltz <it****@gmail.c omwrote:

I've got a form element (a wizard, actually) which is giving me
problems when I try to invoke some of its methods from one of the
methods of a filesystemwatch er. Basically the watcher sits there
waiting to see the file and then it's supposed to go to the next page
(wizard1.Next() ).

I get an InvalidOperatio nException when I do this, though, and as near
as I can tell it's because the watcher creates a new thread and it's
trying to access the form object from a different thread. I don't know
how to fix this, though. Any ideas?

See http://pobox.com/~skeet/csharp/threads/winforms.shtml

Basically, you need to use Control.Invoke/BeginInvoke.

<snip>

Is there any way to force a FileSystemWatch er to use the same thread
it's started in?

You can set the SynchronizingOb ject property to be one of your
controls. That way I believe the calls should end up on the UI thread.

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

[Ian Toltz]

On Mar 15, 4:30 pm, Jon Skeet [C# MVP] <[e-mail] wrote:

Ian Toltz <ito...@gmail.c omwrote:

I've got a form element (a wizard, actually) which is giving me
problems when I try to invoke some of its methods from one of the
methods of a filesystemwatch er. Basically the watcher sits there
waiting to see the file and then it's supposed to go to the next page
(wizard1.Next() ).

I get an InvalidOperatio nException when I do this, though, and as near
as I can tell it's because the watcher creates a new thread and it's
trying to access the form object from a different thread. I don't know
how to fix this, though. Any ideas?

Seehttp://pobox.com/~skeet/csharp/threads/winforms.shtml

Basically, you need to use Control.Invoke/BeginInvoke.

<snip>

Is there any way to force a FileSystemWatch er to use the same thread
it's started in?

You can set the SynchronizingOb ject property to be one of your
controls. That way I believe the calls should end up on the UI thread.

--
Jon Skeet - <[e-mail] >http://www.pobox.com/~skeet Blog:http://www.msmvps.com/jon.skeet
If replying to the group, please do not mail me too

That helped a lot and I got it working. Man, that's some weird stuff.

Anyways, thanks a ton!