Roslyn Code Lens
@MarcelRoozekrans
Overview
What is Roslyn Code Lens?
A Roslyn-based MCP server that gives AI agents deep semantic understanding of .NET codebases — type hierarchies, call graphs, DI registrations, diagnostics, and more. It is built for AI-assisted development tools working with .NET solutions.
How to use Roslyn Code Lens?
Install as a .NET global tool with dotnet tool install -g RoslynCodeLens.Mcp, or use via dnx in VS Code/Visual Studio. The server auto-discovers .sln files by walking up from the current directory, or you can pass a solution path directly, e.g., roslyn-codelens-mcp /path/to/MySolution.sln.
Key features of Roslyn Code Lens
- Semantic type hierarchy and inheritance analysis
- Cross-referencing call sites and symbol references
- Dependency injection registration scanning
- Compiler diagnostics and code fix suggestions
- Dead code detection and complexity metrics
- Source generator output inspection
Use cases of Roslyn Code Lens
- Analyze type hierarchies and inheritance relationships in a solution
- Detect dead code and unused symbols across projects
- Review compiler diagnostics and apply available code fixes
- Inspect dependency injection registrations and service lifetimes
- Identify circular dependencies in project or namespace graphs
FAQ from Roslyn Code Lens
What are the runtime requirements?
.NET 10 SDK and a .NET solution with compilable projects are required.
How does the server discover my solution?
It automatically walks up from the current directory to find .sln files, or you can pass the solution path as a command-line argument.
Does it support hot reload?
Yes. The server watches .cs, .csproj, .props, and .targets files. Affected projects are lazily re-compiled on the next tool query.
What performance can I expect?
Most queries complete in microseconds to low milliseconds after a one-time solution load of about 928 ms (benchmarked on an i9-12900HK with .NET 10.0.3).
How do I install Roslyn Code Lens?
You can install it as a .NET global tool, use the dnx command in VS Code/Visual Studio, or run claude install gh:MarcelRoozekrans/roslyn-codelens-mcp for Claude Code.
