Question

It’s been ages since I’ve written a COM dll. I’ve made a couple of classes now, that inherit from some COM interfaces, but I want to test it out. I know I have to put a GUID somewhere and then register it with regsvr32, but what are the steps involved?

Edit: Sorry, forgot to mention I’m using C++.

Answer 1

To create a new ATL COM project you can proceed as follow:

1. File/New Project
2. Visual C++/ATL/ATL Project
3. Customize it settings, and press finish when done

You have created a new dll, but it is empty, to add a COM object you can do this:

1. Project/Add Class
2. Visual C++/ATL/ATL simple object, press add
3. Give the name you want (like MyObject), and press finish to add it

If you want that an object implement an interface

1. In the class view select the object class (CMyObject)
2. Right click/Add/Implement Interface…
3. You can select which Interface will implement
   1. From an .idl file already in your projects files
   2. From a .tlb/.dll/.exe which have a type library embedded
   3. From an object already registered
4. When done press finish

PS: It is much easier to create a new ATL project with the same name in a different folder, and add the files you have customized. The wizard does several tasks and create several customized files.

For larger projects that are difficult to add file by file, I do the same but instead of adding my files to the new project I start copying the settings from the new projects to the old one, and adding any additional file that the wizard has created and fixing headers like stdafx.h to merge the new settings.

PPS: If you want that your dll to support MFC, instead of selecting ATL Project you have to select MFC/MFC Dll. When you add the ATL Simple Object the wizard will ask to add ATL support to the project.