Before starting any migration from Visual Basic 6.0 to the .NET Framework (either VB.NET or C#), we always recommend that our clients perform at least a couple of pre-migration tasks that help streamline a potential migration process. Here is a brief summary of some of them:
- Code Cleanup: Sometime we run into applications that have modules that haven't been used in a while, and nobody really knows if they are still in use. Going through a Code Cleanup stage greatly helps reduce the amount of code that needs to be migrated, and avoids wasting effort in deprecated parts
- Code Advisor: It is also recommended that you execute Microsoft's Code Advisor for Visual Basic 6.0. This Visual Studio plug-in analyzes your VB6 code and points out programming patterns that present a challenge for the migration to .NET. Some of these patterns are automatically resolved by the VBUC, but even then, you should always use this rule of thumb: if you use high quality VB6 code as input for the VBUC, you get high-quality .NET code as output. Here is a brief example of the suggestion you'll get from the Code Advisor:
- Arrays that are not based on a zero index: Should be fixed in VB6
- Use of #If: Only the part that evaluates to "true" will be converted. This may cause problems after the conversion
- Use Option Explicit and Late binding, declare X with earlybound types: The VBUC is able to deduce the data types of most variables, but if you have an opportunity to fix this in VB6, you should take advantage of it
- Trim, UCase, Left, Right and Mid String functions: The VBUC is able to detect the data type being used and interpret the function (for example, Trim()), as a correct string function (in the example, Trim$()). It still recommended that you fix it before performing the migration.
There are other tasks that may be necessary depending on the project and client, like developing test cases, training the developers on the .NET Framework, preparing the environment, and countless other specific requirements. But if you are considering a .NET migration, you should at the very least take into consideration performing the tasks mentioned above.