In it March issue, Visual Studio Magazine published an in-depth article about legacy migrations called “Unlocking Legacy Code”. This article talks about the challenges faced by companies migrating from Visual Basic 6.0 to .NET, the drivers behind these migrations and the pros and cons of using an automated migration solution.
The article uses BEMAS Software as a case study for successful migration products. I am incredibly happy they are doing as well as they are with the conversion – they are using our tools, and I visited BEMAS about a year and a half ago to train them on the VBUC and help them plan the migration project. I remember they had a lot of conditional statements (by “a lot”, we are talking thousands of different combinations), as mentioned in the article:
"We also ran into some issues with the conversion tool because early on in the VB code we did a lot of #ifs, which means that the code acts differently depending on how you compile it," Pownall adds. BEMAS worked with ArtinSoft so that VBUC would recognize those instances and convert the code correctly.
It was quite a challenge to get it to convert, since the default behavior of the VBUC is to convert the code inside the conditional statement that evaluates to “TRUE”. Commenting out the conditionals wasn’t going to work either, since that would cause multiple variable declarations and other semantic errors that caused issues during the migration of this particular code. In the end we worked together with BEMAS, and with heavy involvement of the VBUC development team, we managed to modify the tool enough to get the code converted correctly.
Another very interesting item mentioned by Steve Pownall in the article, that I want to talk about some more, is the fact that even though the code came through very cleanly, it didn’t have the .NET architecture they were aiming for so they had to “The dev team had to massage or opted to rewrite the rest of the codebase manually in C# and .NET 3.5 using VS2008.”. This is a very important point, since the overall architecture of the code will remain as it was in VB6.0. The migration, however, gets you quickly to a stable .NET codebase that you can then rework to make it take advantage of the latest features of the .NET Framework. In our experience, this path (migrate, then enhance) is the one with the lowest risk, and it allows you to reduce the time to market for your applications by a wide margin. This is important to keep in mind, since we, as developers, always want to improve the code base – it is part of our professional formation, and I would say, part of our nature – but we sometimes fail to grasp the additional risk this implies. The migration is very controlled process, that gets you predictable results in a short time. Enhancing the application after the migration may seem like duplicating work (and indeed, there are enhancements that can be done during the migration process) but it guarantees that you will get a .NET in the allocated timeframe and budget, not to mention the cost advantage.
Read the complete article, Unlocking Legacy Code at Visual Studio Magazine.