import dll file ?

hi..
i got mifare software written in vb.

there are dll file, and a bas file. Seems that the bas file import/declare functions that provided by the dll file.
what is the really use of bas file ?
how can i extract functions in dll file by using c# ?
- i tried to import the dll file, it said that "it is not a COM component..
i'm new to all of this.
can anyone give any brief explanation or solution to my C# ?

sorry for my bad english
thx for reading

If your library is not a COM component then the functions it contains will have to have been exported for you to use them, and you'll have to declare them as external function using the DllImportAttribute class, just like Windows API functions.