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I'm new to all this ActiveX technolgy and I'd like to ask a few questions:
1) When do I use a DLL and when do I use a .EXE?
2) I take it that with a DLL I can have forms in my project? With a .EXE not?
3) I get mixed up when Dim CNEW AS NEW CLASS must be added to the project - Declarations or when an instance of the COM is created?
4) When do I create a .Bas module and set is as startup?
Thanks!
dll are in process components, activex exe are out of process components. That means, you use dll when you do not plan to have remote components (components running on other machines consuming those machines resources instedad of yours). This is in general (Com and DCom technology), but you can make remote components as Dll if you use, for example, MTS. And you may build an activex exe which run on your machine as the other dll and standard exe...
You may have forms in dll and in activex exe. Be careful when using, as your components will have matter on closing if one of those forms does not unload and set to = nothing...
Dim CNEW AS NEW CLASS is a bit dangerous: it means a new instance of CLASS is created every time in your code you refer to it. I do prefer to code
(it is only the way I am used, but as sintax supports the previous, I must think there should be plenty of situations where you could prefer the first)
dim CNEW as CLASS
and, where I need:
set CNEW = new CLASS 'if new instance is required every time
or
set CNEW = CLASS ' if only 1 is required
...
and then
set CNEW = Nothing
to terminate the instance and do not forget "open" components
Sometimes it happen a standard exe should starts form Sub Main added to a bas module. It never happened in a DLL or activex Exe (you have the initialize event of a class for that),. Cases where when proigram should act differently in case a parameter was passed at start up (search for "Command$" in help), or to set compiled options (search for "#If" in help), or to search for previous instances of program and if found exit the standard EXE before showing windows or load heavy components (pure code is quicker).
So far for my knowledge. Let's see if someone else add.
Best regards,
Cesare Imperiali
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