CodeBehind is a modern back-end framework under ASP.NET Core.
YAF.NET - C# ASP.NET Forum
Open source MVVM framework for Web Apps
NBi is a testing framework (add-on to NUnit)
The Open Toolkit library is a fast, low-level C# wrapper for OpenGL
A simple object mapper for .Net
Linq to database provider
Open source and cross-platform machine learning framework for .NET
Open Brush is the community led successor to Tilt Brush!
AI Multi-Agent Framework in .NET
Versatile OpenID Connect stack for ASP.NET Core and Microsoft.Owin
A web application framework
Tools and libraries to glue C/C++ APIs to high-level languages
Download ScriptAnalyzer from PowerShellGallery
Elastic APM .NET Agent
.NET Interactive takes .NET and embeds it into your experiences
A toolkit that helps developing/prototyping VR apps
No ceremony, just code. Blazing fast, typesafe binary serialization
A collection of 500+ analyzers, refactorings and fixes for C#
Fluent migrations framework for .NET
A Json based Rules Engine with extensive Dynamic expression support
A lightweight text templating library written in C#
Svelto ECS C# Entity Component System
Extensions to LINQ to Objects
A set of .NET libraries for Windows implementing PInvoke calls