Sidebar: Advice From the Source

Microsoft advises companies to evaluate the code quality and business value of their Visual Basic 6 applications when deciding if it's worth the effort to migrate them to the .Net development platform.

The company says migration exercises have shown that the overwhelming factors in predicting the success of a migration project are the initial quality of the code and the developers' experience in working with the .Net Framework.

Developers are advised to first migrate a VB6 application in discrete pieces, such as the presentation layer, and run the rest of it through the COM Interop feature.

In its white paper titled "Visual Basic Application Migration Strategy," Microsoft notes the following four modernization options for complete applications or parts of applications. The company says that many enterprise applications will use more than one of these strategies.

Migrate: Chances are that a VB6 application can be migrated if it meets current business needs and the code quality is good. Jay Roxe, a VB product manager, says work done with about 30 enterprise customers at Microsoft's labs in Redmond, Wash., has shown that 60% to 90% of the VB6 code can be migrated to .Net using the code adviser and upgrade wizard.

Reuse: If the application contains well-factored business logic that won't migrate well, those pieces can be used through COM Interop while others are migrated.

Rewrite: If a VB6 application lacks the structure and quality to be effectively migrated, developers should mine and analyze the business rules and data structures to provide the starting point for the rewrite.

Replace: If VB6 code quality is poor and the application isn't critical to the business, an off-the-shelf package might be a good option if it provides at least half of the needed functionality. Outsourcing is another option.

Copyright © 2005 IDG Communications, Inc.

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