Developing the Upgrade Plan

Developing the Upgrade Plan

Once you have determined which projects to upgrade, the rest of the process becomes a whole lot easier. Keep one thing in mind when working out your upgrade plan: If your application consists of a number of projects, some of which depend on others, upgrade the client project first. Next upgrade the project the client depends on. If this project in turn depends on another project, upgrade the more fundamental one next, and so on. Doing the upgrade in this order means you are moving up the dependency hierarchy. Why choose this order? For the simple reason that it s the easiest upgrade path. Using COM components from Visual Basic .NET is simpler than using .NET components from Visual Basic 6. The latter option requires changing both the .NET component and the COM component at the same time. It also means dealing with GUID and versioning issues that can make COM development a complicated process. Starting with the client and moving up the dependency hierarchy keeps all of the COM GUIDs the same and avoids COM versioning issues.

Keeping that rule in mind, you ll find that the rest of the process is simple. Break your application down into its core components, and work out the dependencies. Starting from the client side, decide what components you will upgrade and in what order, and the extent to which each of them will be upgraded (none, partial, full, interop). Large applications will no doubt be handled in stages, since attempting to pull off a full upgrade of all components would be extremely disruptive and would lead to all sorts of testing problems and new bugs. Try to go step by step, testing as you go, to ensure that you maintain a high level of quality.