Roslyn is Microsoft’s brand-new implementation of the C# and VB compilers shipping with Visual Studio 2015. Instead of treating the compiler as a black hole where source code goes in and binaries come out, Roslyn exposes all parts of the compiler, from parsing to code generation, through a clean and consistent API. Among other things, Roslyn makes it very easy for anyone to add analyzers (think errors and warnings) and code fixes (to correct those errors in the IDE) to the C# compiler. If you’re developing a library, you should provide analyzers and code fixes to make using your library easier. Roslyn makes it possible. John Robbins demonstrates how.