Hi,
I get "error LNK2005:" when I build my source code.

Below is what I did:

Main.cpp

#include Main.h
Function();

Main.h

#include "File1.h"
//#include "File2.h"

File1.cpp

#include "File1.h"
void Function()
{
	// Do something
}

File1.h

extern void Function()

File2.cpp

#include "File2.h"
void Function()
{
	// Do something
}

File2.h

extern void Function()

What I'm trying to do is I want to be able to run Function() from File1.cpp when I #include "File1.h" and comment #include "File2.h" in Main.h and run Function() from File2.cpp when I do the opposite. This is to give me the flexibility to change what my program do by just changing the file included instead of modifying my source code.
Please advice.
Thanks.