So things like Environment.PathSeperatorCharacter are just added for the lulz?
MonoDevelop, on *nix, with QT bindings or whatever the hell you want to use is completely seperated from Windows. Not to mention that OP was referring to C# the ECMA and ISO platform agnostic language, which runs on top of the equally platform agnostic CLI.
Yeah, Microsoft also provides some Windows specific runtime libraries. Just like they do for their C++ compiler (MFC). Does this make GCCs C++ any less viable for cross platform development? Of course not, you stupid, trolling, bearded, hippy git.