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DLL Declaration

Posted on 2000-04-12
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Last Modified: 2010-05-02
This guy made his own dll AceVB.dll he declared it in this project:

Declare Function AceTimer Lib "AceVB.dll" () As Integer

He didn't declare the full path to the dll, so I was wondering how you can get away with this. Does registering the dll allow you to access it this way (by just using it's name and not it's path).

Also, this seems stupid to me becsuase if the answer is yes, then why not get a reference on it in the project and use it like an object in your project.
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Question by:tyy8
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7 Comments
 
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Expert Comment

by:Éric Moreau
ID: 2708674
You can't register that kind of DLL.

To access it, the DLL must be place in a folder of your path (type Path a the command prompt).
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peteyhiggins earned 50 total points
ID: 2708855
For certain directories on your computer, the operating system automatically looks in those to see if a dll or exe is present in them.

C:/winnt/system32 is an example of this on Windows NT.

That's why when you want to unregister a DLL, you can type regsvr32 name.dll.  This calls the regsvr32 application that's located in the sytem32 directory, even though you don't have to specify which directory regsvr32 is in, your computer automatically looks for it there.

To see this, on a Windows NT computer, right-click My Computer, go to properties and click the environment tab.  There are listings for both System Variables and User Variables.  Both of these have a path listing that will show you all of the folders that the computer looks in to find dlls and exes.

Peter

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Author Comment

by:tyy8
ID: 2709164
Okay, but is it possible to declare your dll that way (like something from the WinAPI) and access that function directly.

To emoreau: Th setup program did register it on my system, so I don't understand what you mean when you say you can't register that kind of dll
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LVL 70

Expert Comment

by:Éric Moreau
ID: 2709203
DLL that are registred are used by automation. To use them, you set a reference to it (Menu Project->References) and instantiate it (dim x as AceVB).

This DLL, can be distributed but is not necessarely registered. Can you register it manually (with regsvr32.exe)?
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Author Comment

by:tyy8
ID: 2717388
I tried and it said it had no entry point, whatever that means.
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LVL 70

Expert Comment

by:Éric Moreau
ID: 2717405
So this means that this DLL isn't refered (found) via the registry. So it it found via the path.

There are 2 kind of DLL.
-Automation
-Function library.

Automation DLL are referenced and use as an object and then access properties and methods.

Function DLL are librairies that you declare like you did to use.

«then why not get a reference on it»
Because you can't reference a function library DLL that isn't registered.
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Author Comment

by:tyy8
ID: 2899502
Answer accepted
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