Visual Basic 6.0 Compatibility Library
If you have used previous versions of Visual Basic, you will notice that Visual Basic .NET introduces several changes to the Visual Basic language and that some familiar functions have seemingly disappeared. These changes were necessary in order to make Visual Basic compliant with the .NET Platform and the common language specification (CLS).
When a Visual Basic 6.0 application is upgraded to Visual Basic .NET, the conversion of some code is impossible due to syntactical or architectural differences. For this reason, functions in the Visual Basic 6.0 Compatibility library (Microsoft.VisualBasic.Compatibility) are used to allow the code to run in Visual Basic .NET without the need for extensive modification. These functions mimic Visual Basic 6.0 behavior while remaining compliant with the common language specification.
Caution Functions in the Visual Basic 6.0 Compatibility library are provided only for use by the upgrading tools. Although it is possible to use this library when writing new code, there is no guarantee that it will be supported in future versions of Visual Basic.