Mono CSharp Compiler as a Service

CSharp Compiler - Mono:
Starting with Mono 2.2 it supports a Compiler Service that applications can consume.

Microsoft is now re-writing C# compiler in C#, as a major (5 years) project Roslyn,

that enables using C# "compiler as a service"

Same (or similar) functionality is available in Mono (.NET clone) for a few years already... 

Applied ScriptCS with Block, Rusbatch and Ralph @ .NET Rocks