For those interested in programming in C# on Linux or have interest in Mono for using Microsoft's .NET, you may be pleased to know that Mono's C# compiler is now C# 4.0 feature complete. Covariance and contravariance, optional parameters, dynamic binding, and other features of the C# 4.0 programming language have now been implemented within Mono. The Mono C# compiler that supports this is not yet in a released version, but you will need to checkout the Mono SVN code.
Confirmation of the C# 4.0 feature completion for Mono was made on Marek Safar's blog
. Information on this Microsoft programming language is available from Wikipedia