Runtime DLL selection

[QUantumAnenome]

I have a program that compiled with A.lib which will load A.dll. Now I want to use B.dll instead. The functions are the same. I have 2 choices, 1) recompile my app with B.lib or 2) rename B.dll as A.dll and replce the old one.

Is there a way, at runtime without needing to recompile my app, to enumerate all the dll's, and then select which one I would like to use?
Say, next year we have a new C.dll, and we want the old app to be able to use it without renaming it or recompiling.

Thanks.

[DJMaze]

yes there is.
You can load dll's dynamicly

HMODULE my_dll = LoadLibrary("A.dll");

After that you must load all ProcAddresses that you need, for example

typedef WINSHELLAPI void (WINAPI *pILFree)(LPCITEMIDLIST pidl);
pILFree ILFree = (pILFree)GetProcAddress(my_dll, MAKEINTRESOURCE(195));

This creates a pointer to the function that is inside the dll.

GetProcAddress() can be used in 2 ways:
#1 by position (INTRESOURCE)
#2 by name GetProcAddress(my_dll, "winampDSPGetHeader2");

the typedef part is used to identify the function as how it is inside the dll.
I think i'm not 100% here so others could addl in or correct me

Then when you don't need the dll anymore you use

FreeLibrary(my_dll);

[QUantumAnenome]

Thanks, this is what I needed, but the LoadLibrary() always fails, regardless of where I copy my DLLs.

[QUantumAnenome]

Ok, LoadLibrary works fine now (silly error), but what do I need to do to get GetProcAddress() to work. I tried the (my_dll, "MyFuncame"), but I think I need a Module Definition File, but don't know what that is or what to put in it.
Thanks for your help!

[QUantumAnenome]

Yeah! After wading through the microsuck docs, I figured it out. Here it is for those who need to know.

How to explicitly link to a DLL:

In the DLL, you have to have 3 things.
1) The DllMain() MUST return true.
2) The function you want to export must have __declspec(dllexport) in front of it.
3) You need a .DEF file with a list of functions you are exporting
(Note that the microsuck docs claim you do not need #3 if you do #2, but it turns out you need them both for some reason.)

#include	<windows.h>

bool WINAPI DllMain(HINSTANCE hInstance, DWORD reason, LPVOID data)
{
	return true;
}

__declspec(dllexport) int Add(int a, int b) 
{
	return (a+b);
}

Here is the .DEF file

LIBRARY	C1
EXPORTS
   Add  DATA

In the app, you do not need any .LIB files that were generated by the DLL project.

// HMODULE worked too, I don't know which is technically correct
HINSTANCE my_dll = LoadLibrary("C1.dll");

// you could also typedef it like  DJMaze did
int (*myadd)(int, int) = (int (*)(int, int))GetProcAddress(my_dll1, "Add");

// use it normally
int foo = myadd(1, 2);

// free it when finished
FreeLibrary(my_dll);