Enums.NET by: Tyler Brinkley

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

EPPlus by: Jan Källman

A library to manage Excel spreadsheets, using OOXML.

ExcelDataReader by: iciobanu

Lightweight and fast library written in C# for reading Microsoft Excel files ('97-2007).

ExcelNumberFormat by: ExcelNumberFormat developers

.NET library to parse ECMA-376 number format strings and format values like Excel and other spreadsheet softwares.

Exceptionless by: Exceptionless

Exceptionless is a cloud based error reporting service that sends your exceptions to https://exceptionless.com and provides aggregated views and analytics.

Exceptionless.Portable by: Exceptionless

[DEPRECATED] Please install the Exceptionless package instead.

ExCSS by: Tyler Brinks

ExCSS is a CSS 3 parser for .NET. ExCSS makes it easy to read and parse stylesheets into a friendly object model with full LINQ support.

ExtendedNumerics.BigDecimal by: https://github.com/AdamWhiteHat

Arbitrary precision decimal class

Fable.Core by: Alfonso García-Caro Núñez

Fable Core Library

FaceRecognitionDotNet by: Takuya Takeuchi

The world's simplest facial recognition api for .NET This library is ported from https://github.com/ageitgey/face_recognition by C#.

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.

FastMember by: Marc Gravell

In .NET reflection is slow... well, kinda slow. If you need access to the members of an arbitrary type, with the type and member-names known only at runtime - then it is frankly hard (especially for DLR types). This library makes such access easy and fast.

FeatureToggle by: Jason Roberts - dontcodetired.com

An antidote to source control branching sickness for .Net developers. A simple library using the Feature Toggle design/release/continuous integration pattern

FirebirdSql.Data.FirebirdClient by: FirebirdSQL

Firebird ADO.NET Data provider

Fizzler by: Atif Aziz Colin Ramsay

Fizzler is a W3C Selectors parser and generic selector framework for document hierarchies.

FlaUI.UIA3 by: Roemer

Library to use FlaUI with UIA3.

FluentAssertions by: Dennis Doomen Jonas Nyrup Xceed

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. Works with .NET Standard 2.0 and higher, .NET Framework 4.7 and higher and .NET 6 and higher. Supports the unit test frameworks MSTest2, NUnit3, NUnit4, XUnit2, XUnit3, MSpec and TUnit. IMPORTANT: This version is free for open-source projects and non-commercial use, but commercial use requires [a paid license](https://xceed.com/products/unit-testing/fluent-assertions/). Check out the [license page](LICENSE) for more information.

FluentFTP by: J.P. Trosclair Harsh Gupta

An FTP and FTPS library for .NET, optimized for speed. Provides extensive FTP commands, file uploads/downloads, SSL/TLS connections and FTP proxies.

FluentMigrator by: Josh Coffman Tom Marien

FluentMigrator is a database migration framework for .NET written in C#. The basic idea is that you can create migrations which are simply classes that derive from the Migration base class and have a Migration attribute with a unique version number attached to them. Upon executing FluentMigrator, you tell it which version to migrate to and it will run all necessary migrations in order to bring your database up to that version. In addition to forward migration support, FluentMigrator also supports different ways to execute the migrations along with selective migrations called profiles and executing arbitrary SQL.

FluentValidation by: Jeremy Skinner

A validation library for .NET that uses a fluent interface to construct strongly-typed validation rules.