Lean Algorithmic Trading Engine by QuantConnect (Python, C#)

Command line parsing, invocation, and rendering of terminal output.

The mobile app vault (iOS and Android).

ML.NET is an open source and cross-platform machine learning framework for .NET.

One framework for creating powerful cross-platform games.

xUnit.net is a free, open source, community-focused unit testing tool for .NET.

Every programmer needs a rubberduck. COM add-in for the VBA & VB6 IDE (VBE).

AutoFixture is an open source library for .NET designed to minimize the 'Arrange' phase of your unit tests in order to maximize maintainability. Its primary goal is to allow developers to focus on what is being tested rather than how to setup the test scenario, by making it easier to create object graphs containing test data.

ASP.NET Core is a cross-platform .NET framework for building modern cloud-based web applications on Windows, Mac, or Linux.

An open source fork of Windows Live Writer

Mono open source ECMA CLI, C# and .NET implementation.

💫 NClient is an automatic type-safe .Net HTTP client that allows you to call web service API methods using annotated interfaces or controllers without boilerplate code.

Build Mobile, Desktop and WebAssembly apps with C# and XAML. Today. Open source and professionally supported.

The best C# command line parser that brings standardized *nix getopt style, for .NET. Includes F# support

.NET for Apache® Spark™ makes Apache Spark™ easily accessible to .NET developers.

EF Core is a modern object-database mapper for .NET. It supports LINQ queries, change tracking, updates, and schema migrations.

Highly performant and modular controls for node-based editors designed for data-binding and MVVM.

Open Source Web Application Framework for ASP.NET Core

Google's Material Design in XAML & WPF, for C# & VB.Net.

A wrapper executable that can run any executable as a Windows service, in a permissive license.

Accept Bitcoin payments. Free, open-source & self-hosted, Bitcoin payment processor.

.NET core API Gateway

Powerful .NET library for benchmarking

A cross-platform plotting library for .NET

:cake: Cake (C# Make) is a cross platform build automation system.

Linq to database provider.