Top Welcoming Open-Source C# Repositories

☢️ Fallout — The C#/.NET Build System

Let MAUI Sherpa guide you through all your .NET MAUI dev environment needs!

Reactor is an experimental set of extensions to WinUI

Simple, secure, reliable agents. Self-hosted. Open source. Built with .NET.

Self-hosted optimization, monitoring (NMS), and security audit tool for UniFi Networks. Includes Wi-Fi Optimizer for wireless health scoring and channel optimization, advanced DNS/VLAN/firewall security checks, config optimization suggestions, centralized WAN and LAN speed test server w/ L2 tracing, CM, ONT, SFP, 5G modem stats +more.​​​​​​​​​​​​​

Remote Procedure Calls for Kerbal Space Program

Open-source platform for building cross-platform native Mobile, Web, Desktop, and Embedded apps from a single C#/XAML codebase. Work from any IDE/CLI with Hot Reload, Visual Designer, MCPs, and Skills built for modern .NET workflows. 200M+ NuGet downloads.

Command line tools for Azure Functions

Free Bootstrap 5 components for ASP.NET Blazor + optional enterprise-level stack for Blazor development (gRPC code-first, layered architecture, localization, auth, ...)

A C# RPC framework built for QUIC, with bidirectional streaming, first-class async/await, and Protobuf support.

A native .NET LLM inference engine and agent runtime for GGUF models. TensorSharp provides a console application, a web-based chatbot interface, iPhone App, and Ollama/OpenAI-compatible HTTP APIs for programmatic access. It supports Windows/MacOS/iOS/Linux with full GPU capability

.NET for the NES game console

Humanizer meets all your .NET needs for manipulating and displaying strings, enums, dates, times, timespans, numbers and quantities

A next-generation platform for diabetes management

A modern, fast and flexible .NET testing framework

Blazor Component Library based on Material Design principles. Do more with Blazor, utilizing CSS and keeping JavaScript to a bare minimum.

Next generation open source Altinn platform and applications.

A C# architecture test library to specify and assert architecture rules in C# for automated testing.

DNN (formerly DotNetNuke) is the leading open source web content management platform (CMS) in the Microsoft ecosystem.

.NET is a cross-platform runtime for cloud, mobile, desktop, and IoT apps.

Bootstrap Blazor is an enterprise-level UI component library based on Bootstrap and Blazor.

Javascript Interpreter for .NET

Open-source cross-platform symbolic algebra library for C# and F#. Can be used for both production and research purposes.

The Firebase SDK for Unity

Open-source web application framework for ASP.NET Core! Offers an opinionated architecture to build enterprise software solutions with best practices on top of the .NET. Provides the fundamental infrastructure, cross-cutting-concern implementations, startup templates, application modules, UI themes, tooling and documentation.

UniGetUI: The Graphical Interface for your package managers. Could be terribly described as a package manager manager to manage your package managers

TypeWhisper for Windows - Local speech-to-text with translation

PixiEditor is a Universal Editor for all your 2D needs

Project Homepage & Forums

The ProteoWizard Library is a set of software libraries and tools for rapid development of mass spectrometry and proteomic data analysis software.

The Roslyn .NET compiler provides C# and Visual Basic languages with rich code analysis APIs.

The original unitystation

PK-Sim® is a comprehensive software tool for whole-body physiologically based pharmacokinetic modeling

.NET for Android bindings for Google's libraries, such as AndroidX, GooglePlayServices, Firebase, and MLKit and their 3rd party dependency libraries.

Welcome to the home of the Hot Chocolate GraphQL server for .NET, the Strawberry Shake GraphQL client for .NET and Nitro the awesome Monaco based GraphQL IDE.

A community-driven touchscreen music game.

Highly Performant & Scalable Ultima Online Server Emulator

.NET for iOS, Mac Catalyst, macOS, and tvOS provide open-source bindings of the Apple SDKs for use with .NET managed languages such as C#

AI Multi-Agent Framework in .NET

Avalonia theme inspired by Semi Design

Supercharged .NET server side development!

Build all of your apps using what you already know and love ❤️

This repository contains set of components extending functionality of the OpenTelemetry .NET SDK. Instrumentation libraries, exporters, and other components can find their home here.

Audio and MIDI library for .NET

MobiFlight is an open source project that allows you to create your own home cockpit for your favorite flight simulator in a flexible, affordable and extremely user-friendly way.

Store securely encrypted backups in the cloud!

the subtitle editor :)

Self-hosted, open-source financial data MCP server for AI agents — SEC filings, XBRL financials, 13F holdings, insider & congressional trades, short interest, FRED, CFTC/CBOE and daily prices across 64 MCP tools. Equibles Cloud adds earnings call transcripts, live quotes, options chains with Greeks, guidance and a screener.

Garnet is a remote cache-store from Microsoft Research that offers strong performance (throughput and latency), scalability, storage, recovery, cluster sharding, key migration, and replication features. Garnet can work with existing Redis clients.