What Is a COM Add-in?
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A COM add-in is a dynamic-link library (DLL) that is specially registered for loading by the Microsoft® Office XP applications. You can build COM add-ins with any of the Office applications in Office XP Developer. In addition, you can create COM add-ins with Microsoft® Visual Basic® or Microsoft® Visual C++®. For more information about these tools, see the Microsoft Developer Network (MSDN®) Web site at http://msdn.microsoft.com.
Note A COM add-in also can be a Microsoft® ActiveX® .exe file for Visual Basic. However, DLLs generally provide better performance than .exe files.
COM add-ins use the Component Object Model that makes it possible for you to create a single add-in that is available to one or many of the Office applications — Microsoft® Word, Microsoft® Excel, Microsoft® Access, Microsoft® PowerPoint®, Microsoft® Outlook®, Microsoft® FrontPage®, or even the Visual Basic Editor. By developing COM add-ins, you can extend the functionality of your Office-based applications without adding complexity for users.
Add-ins, Templates, Wizards, and Libraries | COM Add-ins vs. Application-Specific Add-ins | Building COM Add-ins for Office Applications | Building COM Add-ins for the Visual Basic Editor | Building Application-Specific Add-ins | Creating Templates | Creating Wizards | Building Reusable Code Libraries