Monodevelop target platform
===

I'm writing a library that is supposed to be cross-platform, but it needs different implementations depending on which platform I want to target. There's also a set of files that I want to include in the project for _every_ target. How can I do this?

EDIT: It's also fine if I can [target a specific .NET runtime](http://monodevelop.com/Download/What's_new_in_MonoDevelop_2.2) (either Microsoft's .NET or Mono), and I've seen the option for this -- its in Build/General in the project options. I'm not sure this is what I need though.