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waf/CSharpRepl

A cross-platform command line C# REPL with syntax highlighting, IntelliSense, NuGet installation and live process attach.

Open-source alternative to:Visual Studio C# Interactive

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What is it?

C# REPL is a command line Read-Eval-Print Loop for experimenting with C# code interactively. It runs on Windows, macOS and Linux as a .NET 10 global tool, and offers IntelliSense with documentation, automatic formatting, and syntax highlighting in the terminal.

Beyond basic evaluation, it can add NuGet packages with the #r directive, reference local assemblies, projects and solutions, and load .csx scripts. Results can be dumped and explored with rich formatting, and IL and lowered C# views are available for the current statement using ILSpy.

The tool can also attach to a running .NET 10 application to evaluate expressions against live state, such as statics and DI services, and replace or wrap methods at runtime using MonoMod. It is intended for development and diagnostics only. Optional AI code completion works with OpenAI, Anthropic, Gemini and other OpenAI-compatible providers using your own API key.

Key features

  • 01Syntax highlighting and IntelliSense with documentation in the terminal
  • 02Install NuGet packages and reference local assemblies, projects or solutions with #r
  • 03Dump and explore objects with formatted, detailed output
  • 04Attach to a running .NET 10 process to inspect state and run code inside it
  • 05View IL and lowered C# for the current statement
  • 06AI code completion with OpenAI, Anthropic, Gemini and other compatible providers

Use cases

  • Quickly testing C# language features or library APIs without creating a project
  • Trying out NuGet packages interactively before adding them to a project
  • Inspecting live state of a development .NET application while it runs
  • Exploring the compiled output of C# code through IL or lowered views

Quick start

  1. 1

    Install the C# REPL global tool from NuGet

    dotnet tool install -g csharprepl
  2. 2

    Run the REPL

    csharprepl

Things to know

  • Requires the .NET 10 SDK or runtime to be installed.
  • Process attach features are for development and diagnostics only and must never be used on production processes.
  • AI code completion needs your own API key from a supported provider.

Topics

#csharp#repl#dotnet#cli#interactive-programming#nuget#console#global-tool

FAQ

What is CSharpRepl?
A cross-platform command line C# REPL with syntax highlighting, IntelliSense, NuGet installation and live process attach. C# REPL is a command line Read-Eval-Print Loop for experimenting with C# code interactively. It runs on Windows, macOS and Linux as a .NET 10 global tool, and offers IntelliSense with documentation, automatic formatting, and syntax highlighting in the terminal.
Is CSharpRepl free to use? What license does it have?
CSharpRepl is open source under the MPL-2.0 license. Check the license terms before using it in commercial products.
Is CSharpRepl still maintained?
Actively maintained. The last commit to CSharpRepl was on Sep 21, 2026.
What can I use CSharpRepl for?
Quickly testing C# language features or library APIs without creating a project Trying out NuGet packages interactively before adding them to a project Inspecting live state of a development .NET application while it runs Exploring the compiled output of C# code through IL or lowered views
How do I install CSharpRepl?
Install the C# REPL global tool from NuGet: dotnet tool install -g csharprepl Run the REPL: csharprepl
Where can I get CSharpRepl?
The source code and installation instructions are on GitHub: https://github.com/waf/CSharpRepl

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