Chapter 5 -- Versioning Components

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Chapter 5

Component versioning is critical in the production environment. To harvest COM's most powerful features, you must be able to revise your servers and replace them in the field without adversely affecting any client applications. This chapter shows you the options that Microsoft Visual Basic gives you to accomplish this. For some readers, this might prove to be the most valuable topic in the book.

We'll examine the most important versioning issues a Visual Basic programmer faces when creating and maintaining components for an application. These guidelines apply whether your application is based on COM+, MTS, or earlier versions of COM. You'll learn when and how to use Visual Basic's binary compatibility scheme. I'll also point out a few important limitations of using binary compatibility and show you an alternative technique for versioning Visual Basic components. This technique involves defining interfaces with Interface Definition Language (IDL) and building custom type libraries.

My goal in this chapter is to arm you with enough knowledge to realize one of COM's biggest promises: the ability to easily maintain and extend your application code once it's been put into production.