If I understand your question correctly, you need C # REPL, but if you are not looking for any REPL on .NET, and Clojure seems like this, since it already has REPL, and there is a Clojure .NET port.
If so, you might consider integrating F # REPL, F # Interactive. Firstly, it was integrated into the MonoDevelop open source development environment , so the source code is available for reference.
Joel mueller
source share