ActiveX DLLs and ActiveX EXEs are almost exactly the same in the ways they are built and used. In both cases, you build one or more classes that applications can use to do something. The big difference lies in where they are used.
An ActiveX DLL's code is executed within the main program's address space. It behaves as if the class was created within the main program's code. Because the code lies inside the program's address space, calling methods is very fast.
An ActiveX EXE's code is run in a separate process. When the main program calls an ActiveX EXE's method, the system marshalls the call to translate the parameters into the ActiveX EXE's address space, calls the method, translates the results back into the main program's address space, and returns the result. This is slower than running an ActiveX DLL's method inside the main program's address space.
Because of the difference in speed, an ActiveX DLL is almost always preferable. The reason ActiveX EXEs are useful is they can run on a different computer than the main program while an ActiveX DLL must run on the same computer as the main program.
If you want to build a library of shared routines to save programming and debugging, use an ActiveX DLL because it will give you better performance. Even if you need to distribute several copies of the DLL on different computers, it will probably be worthwhile.
If you want a centralized server library, use an ActiveX EXE. The EXE can sit on a central computer and work directly with that computer's resources. If you need to frequently change how the code works, you can easily change it in one place.
Reply With Quote
