.NET does have the module level directive "InternalsVisibleTo" that declares another assembly as a friend assembly that can use internal API's from the first assembly. So if you have e.g MyLib.Core and then two impls on top say MyLib.Windows and MyLib.OSX, where everyone would only use one of the impl libs but always the core lib (which is why it was split - then you could make internal API in the core lib visible ONLY to the Windows/OSX libs by using InternalsVisibleTo, and users of the library could not see that internal API.
Yep, that is what I meant by mentioning .NET in "This is nothing new to Java, other languages e.g. Ada, Delphi, .NET and even Go have this kind of visibility concept."
