DotNetOpenAuth.OpenId.RelyingParty by: Andrew Arnott

Increase conversion rates to your web site by lowering the bar to create an account with your site, by allowing customers to use accounts they already have with other sites, such as Google and Yahoo!

Dynamitey by: Dynamitey

(pronounced dyna-mighty) flexes DLR muscle to do meta-mazing things in .net

EntityFramework by: Microsoft

Entity Framework 6 (EF6) is a tried and tested object-relational mapper for .NET with many years of feature development and stabilization.

Enums.NET by: Tyler Brinkley

Enums.NET is a high-performance type-safe .NET enum utility library

envdte by: Microsoft

A member of the Visual Studio SDK

envdte100 by: Microsoft

A member of the Visual Studio SDK

envdte80 by: Microsoft

A member of the Visual Studio SDK

envdte90 by: Microsoft

A member of the Visual Studio SDK

envdte90a by: Microsoft

A member of the Visual Studio SDK

ExtendedNumerics.BigDecimal by: Adam White Jan Christoph Bernack Rick Harker

An arbitrary precision decimal (base 10) floating point number type using a mantissa and exponent. Supports nth roots, trigonometric functions, logarithms, natural e, pi, etc.

FaceIT.Hangfire.Tags by: Erwin Bovendeur

Add tags to Hangfire backgroundjobs

FakeItEasy by: Patrik Hägne FakeItEasy contributors

It's faking amazing! The easy mocking library for .NET that works great in C# and VB.NET alike. No need to know the difference between a stub, a mock or a spy, everything's a fake! The easy to use, refactoring friendly API makes faking a breeze.

FakeXrmEasy by: @jordimontana

Utilities to streamline unit testing in Dynamics CRM 2011 by faking the IOrganizationService against an In-Memory context which runs blazingly fast.

FakeXrmEasy.365 by: @jordimontana

Utilities to streamline unit testing in Dynamics CRM 365 by faking the IOrganizationService against an In-Memory context which runs blazing fast.

Fare by: Nikos Baxevanis

.NET port of dk.brics.automaton - Project Fare is an effort to bring a DFA/NFA (finite-state automata) implementation from Java to .NET. There are quite a few implementations available in other languages today. This project aims to fill the gap in .NET.

FirebaseAdmin by: Google Inc.

Firebase Admin SDK enables server-side .NET developers to integrate Firebase into their services and applications.

FluentAssertions by: Dennis Doomen Jonas Nyrup

A very extensive set of extension methods that allow you to more naturally specify the expected outcome of a TDD or BDD-style unit tests. Targets .NET Framework 4.5 and 4.7, as well as .NET Core 2.0, .NET Core 3.0, .NET Core 2.1, .NET Standard 1.3, 1.6, 2.0 and 2.1. Supports the unit test frameworks MSTest, MSTest2, Gallio, NUnit, XUnit, MBUnit, MSpec, and NSpec.

FluentCommandLineParser by: siywilliams

A simple, strongly typed .NET C# command line parser library using a fluent easy to use interface

FluentFTP by: Robin Rodricks FluentFTP Contributors

An FTP and FTPS client for .NET & .NET Standard, optimized for speed. Provides extensive FTP commands, File uploads/downloads, SSL/TLS connections, Directory listing parsing, File hashing/checksums, File permissions/CHMOD, FTP proxies, FXP transfers, UTF-8 support, Async/await support, Powershell support and more. Written entirely in C#, with no external dependencies.

FluentScheduler by: Jim Geurts <jim@biacreations.com> Talles L <talleslasmar@gmail.com> & further contributors

Automated job scheduler with fluent interface.