I recently tried using a Tuple in one of my submissions (I won't say which one since it ended up being the wrong move) and got a compiler error. I'm seeing System.Tuple in Mono documentations online and have no issues with using it in MonoDeveloper(Xamarin), but here I get

Invocation failed [COMPILATION_ERROR] Can't compile program.cs: program.cs(11,13): error CS0103: The name `Tuple' does not exist in the current context

Is this a C# 2.0 issue? Seems like it shouldn't be... I mean the (x)=>x.y lambdas seem to work?

Anyone have any ideas? Also, where should I go to see an entire usable library compatible with all the components used by CodeForces for C#, so that I don't hang myself with unsupported classes again in the future?

Thanks