ExcelDataReader by: ExcelDataReader developers

Lightweight and fast library written in C# for reading Microsoft Excel files (XLS, XLSX).

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.

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.Signed 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.

FastReport.OpenSource by: Fast Reports Inc.

FastReport Open Source provides a free report generator for .NET/.NET Framework. You can use the FastReport Open Source in MVC, Web API, console applications. FastReport is written in C# and it is compatible with .NET Framework 4.6.2, .NET 6 and higher. Extendable FastReport architecture allows creating your own objects, export filters, wizards, and DB engines. - FastReport is a band-oriented report generator. There are 13 types of bands available: Report Title, Report Summary, Page Header, Page Footer, Column Header, Column Footer, Data Header, Data, Data Footer, Group Header, Group Footer, Child, and Overlay. In addition, sub-reports are fully supported. - A wide range of band types allows creating any kind of report: list, master-detail, group, multi-column, master-detail-detail and many more. - Wide range of available report objects: text, picture, line, shape, barcode, matrix, table, checkbox. - Reports can consist of several design pages, which allows reports to contain a cover, the data and a back cover, all in one file. - The Table object allows building a tabular report with variable number of rows and/or columns, just like in MS Excel. Aggregate functions are also available. - Powerful, fully configurable Matrix object that can be used to print pivot tables. - Report inheritance. For creating many reports with common elements such as titles, logos or footers you can place all the common elements in a base report and inherit all other reports from this base. Data Sources: - You can get data from XML, CSV, JSON, MS SQL, MySQL, Oracle, Postgres, MongoDB, Couchbase, Raven DB, SQLite. - FastReport has the ability to get data from business objects of IEnumerable type. - Report can contain data sources (tables, queries, DB connections). - Thus, you can not only use application-defined datasets but also connect to any database and use tables and queries directly within the report. FastReport Open Source can save documents in HTML, BMP, PNG, JPEG, GIF, TIFF, EMF. PDF export is available as a plugin.

ExcelNumberFormat by: ExcelNumberFormat developers

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

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

Arbitrary precision decimal class

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.

FastReport.Compat by: Fast Reports Inc.

Common compatible types for FastReport .Net, Core and Mono

FirebaseAdmin by: Google Inc.

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

Fizzler by: Atif Aziz Colin Ramsay

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

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.

FirebirdSql.Data.FirebirdClient by: FirebirdSQL

Firebird ADO.NET Data provider

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.

FluentValidation.ValidatorAttribute by: Jeremy Skinner

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

FluentValidation by: Jeremy Skinner

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

Flurl.Http by: Todd Menier

A fluent, portable, testable HTTP client library.

FodyHelpers by: The Fody Team

Helpers for Fody.

Flurl by: Todd Menier

A fluent, portable URL builder. To make HTTP calls off the fluent chain, check out Flurl.Http.

Fody by: The Fody Team

Extensible tool for weaving .net assemblies.