Introduction to AddIns

Office provides a number of patterns to extend the functionality of Office applications. The most common patterns are these:

• Office automation executables

• Office add-ins

• Code behind an Office document or template

This chapter covers how to write COM add-ins in Visual Basic for Word and Excel. It also describes how COM add-ins are registered in the registry and why there is another step, called shimming, that must be taken before deploying a managed COM add-in.

VSTO supports building a new kind of "VSTOstyle" add-in for Outlook 2003. The VSTO Outlook add-in project is the preferred way to build Outlook add-ins for Outlook 2003 and is described in Chapter 24, "Creating Outlook AddIns with VSTO." The VSTO Outlook add-in project fixes many of the issues in COM add-in development discussed in this chapter, as well as some additional Outlookspecific issues. The only reason to write a managed COM add-in for Outlook following the instructions in this chapter is if it must run in versions of Outlook older than Outlook 2003.