Hi,

I have a problem using a ManuelResetEvent in the GUI thread while receiving 
events from the Shell (new folders, rename etc).

This is what i do:

Receiving an event from the Shell.
Running some code - setting ManauelResetEvent.Reset().
The code continue - and somewhere else i test the handle 
"ManuelResetEvent.WaitOne(100, true)" - still in the GUI thread.
While waiting (in WaitOne), the application receive yet another event from 
the Shell - also in the main thread.

How is it possible to receive the second event while blocking the GUI thread 
??

Thank you in advance
BR
Peter

Hi Peter,

Sorry for delayed reply. 

Could you please tell me more about your scenario? Are you watching for 
file system changes? Preferrably a simple but complete and reproducible 
project will be great for quick troubleshooting. Thanks.


Regards,
Walter Wang (wawang@online.microsoft.com, remove 'online.')
Microsoft Online Community Support

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Hi Walter,

I will try to create a small demo project within a few days !!

/Peter

First - I don't know a great deal about the shell messages in 
question, so this only covers general principal...

I think part of the problem is that blocking the UI thread is never a 
good idea.

Would it be possible to simply disable the UI (i.e. set .Enabled = 
false on a few strategic controls), do the waiting on a pool thread, 
and then call-back (Control.Invoke) onto the UI thread to wake it all 
back up and re-enable the UI?

Alternatively, Application.DoEvents() exists, which should allow it to 
process enough of the message-queue to get your external messages - 
but you can't really predict what messages it is going to handle doing 
this. I would tend to use the first approach if possible.

Marc

Hi Marc,

Shell events don't differ from invoking to the GUI thread.

What i don't understand is that while blocking the GUI thread, the GUI 
thread decides to continue somewhere else. And i'm not talking about holding 
the thread for a long time of periode, WaitOne(0, true) would also raise 
this issue.

/Peter

Ahah! it becomes clearer... I read the line (below) as "this is what I 
want to achieve", rather than "this is darned freaky, why is it 
happening?"


> How is it possible to receive the second event while blocking the 
> GUI thread ??


Yes, that is odd... are you sure that it is actually the GUI thread 
that is invoking? It could be the shell events are arriving on an 
arbitrary thread? Worth checking the ManagedThreadId in the GUI code, 
and in the method that is being triggered... are they 
one-and-the-same?

Marc