Was C# compiler written in C++?

Question

Was C# compiler written in C++?

Answer 1

There is a new (as of late 2011) C# and VB compiler written by Microsoft called Roslyn which is written in C# and VB.NET respectively. Project page is here. The Roslyn compiler is written as a library that exposes a rich public API. There is a news article here about it from InfoWorld.

UPDATE: As of April 3, 2014, Roslyn is open source under the Apache License 2.0.