Passing in multiple class libraries of different types to a method

I haven't had to do this for years and forget how.

I have a method that I want to sometimes run with one library and sometimes another. Other than the library I'm using, the method is exactly the same. The same deletion handling, file handling everything.

How do I pass in a library to a method and let the method accept either library?

asp.net vb.net but C# is fine if that's all you've got.

Thanks!