Perhaps (hopefully) I’m missing something obvious, but I can’t see from the Mono site what version of C# is used for any particular version of Mono, and as a C# newbie I’m not sure how to find out directly myself.
My specific question is: what version of C# is used by Mono 2.6.4? (The reason I’m interested in that version is that it seems to be the base version of the Mono variant used by the current version of Unity 3D.)
The release notes have this to say:
So, to be safe, keep to C# 3.0 features.