In Visual Studio "14", the C# and VB compilers and IDE support are fully built on the .NET Compiler Platform ("Roslyn"). This open-source compiler as a service now sits behind dozens of developer experiences in Visual Studio "14", powering build, IntelliSense, refactoring, CodeLens, debugging and many more features developers use every day. In most places the experiences are unchanged, but there have also been many small improvements across the entire development experience as part of the new compiler platform.

Microsoft
C#
HTML
F#
VB.NET
Roslyn
C++
VB
vNext