HOWTO: Change ClassName of running app or change classname of app during launch

[Mike Paschen]

I have an app that checks for its classname to prevent launching a 2nd
instance but I really need to launch a 2nd instance of it. Therefore I'd
think that I either need to change the classname of the running app or
change the classname of the 2nd instance while I launch it. Any ideas how to
accomplish this?

I've checked into GetClassInfoEx and GetClassLong and can retrieve all the
class information of the running application but SetClassLong doesn't allow
me to change the name. I also looked into RegisterClassEx where I can set
the classname in the WNDCLASSEX structure but don't understand how (if
possible) to use it with CreateWindowEx. CreateProcess doesn't seem to have
an option of setting the classname either.

I'd appreciate any help you can give me.

Mike

[Mark Alexander Bertenshaw]

Mike -

Are talking about the class of the top level window? I was led to believe
that all VB forms had roughly the same class name, e.g. ThunderForm,
VB5ThunderForm, etc.
Is there any particular reason why you need to use this mechanism for
checking whether a previous instance of your application exist? Why not use
App.PrevInstance?

---------------------------------------
Mark Alexander Bertenshaw
Programmer/Analyst
Prime Response
Brentford
UK
"Mike Paschen" <mike@leadman.net> wrote in message
news:38d9b1cb$1@news.devx.com...
> I have an app that checks for its classname to prevent launching a 2nd
> instance but I really need to launch a 2nd instance of it. Therefore I'd
> think that I either need to change the classname of the running app or
> change the classname of the 2nd instance while I launch it. Any ideas how
to
> accomplish this?
>
> I've checked into GetClassInfoEx and GetClassLong and can retrieve all the
> class information of the running application but SetClassLong doesn't
allow
> me to change the name. I also looked into RegisterClassEx where I can set
> the classname in the WNDCLASSEX structure but don't understand how (if
> possible) to use it with CreateWindowEx. CreateProcess doesn't seem to
have
> an option of setting the classname either.
>
> I'd appreciate any help you can give me.
>
> Mike
>
>

[Alan Gillott]

I think he means, he has an app that only allows one instance, but he'd like
it to run a second instance only if the class name was different. If the
class name is the same he wants it to fail as it is meant to.
As i see it, he has to make a copy of the program and clone the associated
registry entries, maybe even patching the copy to ensure it doesn't blow the
registry of the original. Can be done but he needs to be painstakingly
careful and find all instances og his clsid and class name in the dll. I
wouldn't like to do it!

Mark Alexander Bertenshaw <Mark.Bertenshaw@virgin.net> wrote in message
news:38daa146@news.devx.com...
> Mike -
>
> Are talking about the class of the top level window? I was led to believe
> that all VB forms had roughly the same class name, e.g. ThunderForm,
> VB5ThunderForm, etc.
> Is there any particular reason why you need to use this mechanism for
> checking whether a previous instance of your application exist? Why not
use
> App.PrevInstance?
>
> ---------------------------------------
> Mark Alexander Bertenshaw
> Programmer/Analyst
> Prime Response
> Brentford
> UK
> "Mike Paschen" <mike@leadman.net> wrote in message
> news:38d9b1cb$1@news.devx.com...
> > I have an app that checks for its classname to prevent launching a 2nd
> > instance but I really need to launch a 2nd instance of it. Therefore I'd
> > think that I either need to change the classname of the running app or
> > change the classname of the 2nd instance while I launch it. Any ideas
how
> to
> > accomplish this?
> >
> > I've checked into GetClassInfoEx and GetClassLong and can retrieve all
the
> > class information of the running application but SetClassLong doesn't
> allow
> > me to change the name. I also looked into RegisterClassEx where I can
set
> > the classname in the WNDCLASSEX structure but don't understand how (if
> > possible) to use it with CreateWindowEx. CreateProcess doesn't seem to
> have
> > an option of setting the classname either.
> >
> > I'd appreciate any help you can give me.
> >
> > Mike
> >
> >
>
>

[Phil Weber]

> I think he means, he has an app that only allows one instance,
> but he'd like it to run a second instance only if the class name
> was different.

Alan/Mark: I think Mike is saying that he has a third-party application (one
that he didn't write, and that isn't necessarily written in VB) that only
allows a single instance, but he's like to be able to run multiple instances
of it. He's trying to figure out a way to trick the app into allowing him to
do so.

Mike: Even if you can figure out a way to do this, it's very dangerous and I
don't recommend it. The app is likely written with the assumption that there
will only be a single instance of it running at any time. Tricking it into
running multiple instances may produce unpredictable results, including
possible corruption of your data. I would suggest contacting the vendor of
the app and seeing if there's some supported way to do this, or simply run
the second instance on a laptop adjacent to your desktop machine. ;-)
---
Phil Weber

[Mark Alexander Bertenshaw]

Mike -

Are talking about the class of the top level window? I was led to believe
that all VB forms had roughly the same class name, e.g. ThunderForm,
VB5ThunderForm, etc.
Is there any particular reason why you need to use this mechanism for
checking whether a previous instance of your application exist? Why not use
App.PrevInstance?

---------------------------------------
Mark Alexander Bertenshaw
Programmer/Analyst
Prime Response
Brentford
UK
"Mike Paschen" <mike@leadman.net> wrote in message
news:38d9b1cb$1@news.devx.com...
> I have an app that checks for its classname to prevent launching a 2nd
> instance but I really need to launch a 2nd instance of it. Therefore I'd
> think that I either need to change the classname of the running app or
> change the classname of the 2nd instance while I launch it. Any ideas how
to
> accomplish this?
>
> I've checked into GetClassInfoEx and GetClassLong and can retrieve all the
> class information of the running application but SetClassLong doesn't
allow
> me to change the name. I also looked into RegisterClassEx where I can set
> the classname in the WNDCLASSEX structure but don't understand how (if
> possible) to use it with CreateWindowEx. CreateProcess doesn't seem to
have
> an option of setting the classname either.
>
> I'd appreciate any help you can give me.
>
> Mike
>
>

[Alan Gillott]

I think he means, he has an app that only allows one instance, but he'd like
it to run a second instance only if the class name was different. If the
class name is the same he wants it to fail as it is meant to.
As i see it, he has to make a copy of the program and clone the associated
registry entries, maybe even patching the copy to ensure it doesn't blow the
registry of the original. Can be done but he needs to be painstakingly
careful and find all instances og his clsid and class name in the dll. I
wouldn't like to do it!

Mark Alexander Bertenshaw <Mark.Bertenshaw@virgin.net> wrote in message
news:38daa146@news.devx.com...
> Mike -
>
> Are talking about the class of the top level window? I was led to believe
> that all VB forms had roughly the same class name, e.g. ThunderForm,
> VB5ThunderForm, etc.
> Is there any particular reason why you need to use this mechanism for
> checking whether a previous instance of your application exist? Why not
use
> App.PrevInstance?
>
> ---------------------------------------
> Mark Alexander Bertenshaw
> Programmer/Analyst
> Prime Response
> Brentford
> UK
> "Mike Paschen" <mike@leadman.net> wrote in message
> news:38d9b1cb$1@news.devx.com...
> > I have an app that checks for its classname to prevent launching a 2nd
> > instance but I really need to launch a 2nd instance of it. Therefore I'd
> > think that I either need to change the classname of the running app or
> > change the classname of the 2nd instance while I launch it. Any ideas
how
> to
> > accomplish this?
> >
> > I've checked into GetClassInfoEx and GetClassLong and can retrieve all
the
> > class information of the running application but SetClassLong doesn't
> allow
> > me to change the name. I also looked into RegisterClassEx where I can
set
> > the classname in the WNDCLASSEX structure but don't understand how (if
> > possible) to use it with CreateWindowEx. CreateProcess doesn't seem to
> have
> > an option of setting the classname either.
> >
> > I'd appreciate any help you can give me.
> >
> > Mike
> >
> >
>
>

[Phil Weber]

> I think he means, he has an app that only allows one instance,
> but he'd like it to run a second instance only if the class name
> was different.

Alan/Mark: I think Mike is saying that he has a third-party application (one
that he didn't write, and that isn't necessarily written in VB) that only
allows a single instance, but he's like to be able to run multiple instances
of it. He's trying to figure out a way to trick the app into allowing him to
do so.

Mike: Even if you can figure out a way to do this, it's very dangerous and I
don't recommend it. The app is likely written with the assumption that there
will only be a single instance of it running at any time. Tricking it into
running multiple instances may produce unpredictable results, including
possible corruption of your data. I would suggest contacting the vendor of
the app and seeing if there's some supported way to do this, or simply run
the second instance on a laptop adjacent to your desktop machine. ;-)
---
Phil Weber