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How to find out if a dll is registered or not ?

Posted on 2006-07-14
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Last Modified: 2010-04-05
Hi.

I'd like to send a command
regsvr32 /u  ***.dll

but only if it is registered.
Is there a way to find out programmatically ?

Thanks in advance.
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Question by:CodedK
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Expert Comment

by:2266180
ID: 17108003
I found this:
http://www.developerfusion.co.uk/show/3479/
and another idea:
http://experts.about.com/q/Visual-Basic-1048/DLL-OCX-Registered.htm
and another thread:
http://forums.winamp.com/showthread.php?threadid=181974 (didn't read throu)

you could also try to move the dll, or to rename it and trap error
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LVL 26

Expert Comment

by:Russell Libby
ID: 17108079

Have you checked out the tip on my site:

http://users.adelphia.net/~rllibby/delphitips/tip8.html

regarding programmatically registering / unregistering a library? You can use this class to determine if a dll exposes the required functions, and there is no problem with unregistering a library that is not registered (most just remove any registry keys they created). The functions return an HRESULT (no error messages, exceptions), so you choose how you want to handle the return, if at all.

Regards,
Russell
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Author Comment

by:CodedK
ID: 17108333
Ciuly thanks, i've read the articles, the source code in DeveloperFusion (Is it in C ?)
probably talks about looking if a dll can be loaded, if it is available...(Maybe i'm wrong...).
But mine is a windows component, its available.
I'd like to learn the current state.

Russell i've tracked the registry changes (registering/unregistering the dll)...
You are right, i can do without regsrv. I can just change the registry keys with you "RegTransfer" unit.

Just to be on the safe side i'd like to try COMREG unit ...
Can you give me an example of how to :
Check if it is available, load it and unload it ?

Thanks :)
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Accepted Solution

by:
Russell Libby earned 250 total points
ID: 17108479
Very simple to use, let me know if you have questions.

Russell


Example:

  with TComRegistration.Create do
  begin
     try
       // Set lib name to the name of the dll you are working with
        if (Load(LibName) = ERROR_SUCCESS) and IsLoaded and IsComLibrary then
        begin
           if (Perform(raUnregister) = S_OK) then
           begin
              ShowMessage('Unregistered');
           end;
        end;
     finally
        Free;
     end;
  end;
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LVL 16

Author Comment

by:CodedK
ID: 17108577
Thank you both :)

Russell it works perfect, i can handle the messages now which is good :)
But more or less it does the same thing as the code in DeveloperFusion, it checks
for the existence of the file...
If it manage to load it then ok it exists... Anyway i can track it through registry and then load itwith your
unit  :)
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