In order to move the Visual Basic language forward, it is necessary to introduce incompatibilities between the Visual Basic 7.0 language and previous versions of Visual Basic. Because of the potential impact of language incompatibilities on users, it is done so only when there is a clear justification. In general, there are only two situations that are considered serious enough to justify an incompatibility:
When designing a feature that is incompatible with previous versions, the ability to upgrade code from previous versions is taken into consideration, but is not an absolute requirement.