I'm attempting to compile some C# with gmcs version 2.11.0 that includes System.Tuple. Supposedly it does exist in Mono (http://stackoverflow.com/questions/5346453/mono-is-there-a-system-tuple) and it is possible to compile using the flag:
gmcs -langversion:future
It doesn't seem to matter which langversion I use, the compiler always gives the same error:
error CS0234: The type or namespace name `Tuple' does not exist in the namespace `System'. Are you missing an assembly reference?
How can I compile C# code using Mono that uses System.Tuple?