Unity / XNA game patcher and plugin framework
Tools and libraries to glue C/C++ APIs to high-level languages
Cross platform code coverage for .NET
NUnit 3 Framework
Core functionality needed to create .NET Core projects
The Twilio SendGrid C# API Library
Framework for building Windows desktop applications
Cross-platform runtime for cloud, mobile, desktop, and IoT apps
An asynchronous, persistent key-value store
A cross-platform UI framework for .NET
An advanced, composable, functional reactive model-view-viewmodel
PeachPie, the PHP compiler and runtime for .NET and .NET Core
Reko is a binary decompiler
Sisk's request and response processor mainframe source code
Cofoundry is an extensible and flexible .NET Core CMS
OpenCV wrapper for .NET
Bing is a framework based on .net core 3.1
A library to support tests with throwaway instances of Docker
A popular high-performance JSON framework for .NET
CacheManager is an open source caching abstraction layer for .NET
A free, open-source, and cross-platform big data analytics framework
A friendly substitute for .NET mocking libraries
Open source web application framework for ASP.NET core
SkiaSharp is a cross-platform 2D graphics API for .NET platforms
YAF.NET - C# ASP.NET Forum