F# has a REPL (read–eval–print loop) F# Interactive, C:\\Program Files (x86)\\Microsoft F#\\v4.0\\Fsi.exe.
C:\\Program Files (x86)\\Microsoft F#\\v4.0\\Fsi.exe
I understand C# now has its own interactive REPL,
Anders Hejlsberg builds a C# REPL loop in this video, 65 minutes in:
http://channel9.msdn.com/Events/PDC/PDC08/TL16#time=65m00s
It's a much older version of Roslyn, but the same ideas apply (and eval! ;).