roslyn-language-server

May 17, 2026 ยท View on GitHub

A Language Server Protocol (LSP) implementation for C# and Razor powered by Roslyn.

Overview

The roslyn-language-server is a .NET tool that provides rich language features for C# and Razor through the Language Server Protocol. It powers editor integrations including the C# extension for Visual Studio Code and C# Dev Kit.

This tool implements the LSP specification, enabling features such as:

  • IntelliSense (code completion)
  • Go to definition
  • Find all references
  • Code fixes and refactorings
  • Diagnostics and errors
  • Hover information
  • Document formatting
  • And more

Installation

Install the language server as a .NET tool:

dotnet tool install --global roslyn-language-server --prerelease

Usage

The language server is designed to be launched by editor clients and typically should not be run directly by end users. It communicates via standard input/output or named pipes.

Command-line Options

All options are optional. One of --stdio or --pipe should typically be specified for communication.

Note: Command-line options are subject to change in future versions.

  • --stdio - Use standard I/O for communication with the client (default: false)
  • --pipe <name> - Use a named pipe for communication
  • --autoLoadProjects - Automatically discover and load projects based on workspace folders (default: false)
  • --logLevel <level> - Set the minimum log verbosity: Trace, Debug, Information, Warning, Error, or None (default: Information)
  • --extensionLogDirectory <path> - Directory for log files
  • --extension <path> - Load extension assemblies (can be specified multiple times)
  • --debug - Launch the debugger on startup (default: false)
  • --telemetryLevel <level> - Set telemetry level: all, crash, error, or off (default: off)
  • And other specialized options for advanced scenarios

Example

roslyn-language-server --stdio --autoLoadProjects

Requirements

  • .NET 10.0 or later runtime

More Information

License

This tool is part of the .NET Compiler Platform ("Roslyn") and is licensed under the MIT license.