Office provides a number of patterns to extend the functionality of Office applications. The most common patterns are these:
This chapter covers how to write COM add-ins in C# 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 2005 supports building a new kind of "VSTO-style" 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 Add-Ins 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 Outlook-specific 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.