Roslyn is a compiler platform that provides C# and Visual Basic with open-source compiler implementations and rich code analysis APIs.
Roslyn solves the problem of enabling developers to build sophisticated code analysis and transformation tools by exposing the compiler's internal structure as public APIs. Rather than treating the compiler as a black box, Roslyn exposes its syntax trees, semantic models, and diagnostic infrastructure, allowing tools to inspect and reason about code at the same level of detail the compiler itself uses. This approach makes it possible to build linters, refactoring tools, code generators, and IDE features that understand code semantically rather than through pattern matching alone.
Roslyn is essential for anyone building C# or Visual Basic development tools, whether as IDE extensions, standalone analyzers, or code generation utilities. It suits projects that need to understand or transform code programmatically with full language semantics. The tool is particularly valuable for teams creating custom linting rules, automated refactorings, or language-aware code generators. The project maintains separate repositories for language feature discussions, directing feature suggestions for C# and Visual Basic to dedicated language repositories rather than handling them in the compiler codebase itself.
Development on Roslyn follows an open contribution model where both core team members and external contributors submit pull requests through the same review process. The project maintains structured guidance for contributors through detailed documentation covering coding guidelines, development workflows including debugging and testing, and a formal API review process for changes to public APIs. The community engages through GitHub Discussions for questions and project sharing, with an active Discord channel for real-time conversation among community members.
