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.

FastEndpoints by: FastEndpoints

A light-weight REST Api framework for ASP.Net 6 and newer that implements REPR (Request-Endpoint-Response) Pattern.

FastEndpoints.Attributes by: FastEndpoints

Attributes used by FastEndpoints.

FastEndpoints.Messaging.Core by: FastEndpoints

Core messaging features used by FastEndpoints.

FastEndpoints.Swagger by: FastEndpoints

Swagger support for FastEndpoints.

FastExpressionCompiler.src by: Maksim Volkau

FastExpressionCompiler is 10-40x times faster than Expression.Compile()

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.

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.

FirebirdSql.Data.FirebirdClient by: FirebirdSQL

Firebird ADO.NET data provider

Fleck by: statenjason

C# WebSocket Implementation

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, MSTest3, MSTest4, 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.

FluentEmail.Core by: Luke Lowrey Ben Cull Github Contributors

Send emails very easily. Use razor templates, smtp, embedded files, all without hassle. This is a Base Package and includes just the domain model, very basic defaults, and is also included with every other Fluent Email package here.

FluentEmail.Smtp by: Luke Lowrey Ben Cull Github Contributors

Now we're talking. Send emails via SMTP.

FluentNHibernate by: James Gregory and contributors (Paul Batum Hudson Akridge Gleb Chermennov Jorge Rodríguez Galán).

Fluent, XML-less, compile safe, automated, convention-based mappings for NHibernate.

FluentScheduler by: FluentScheduler

Automated job scheduler with fluent interface.

FluentStorage by: Robin Rodricks Ivan Gavryliuk FluentStorage Contributors

FluentStorage, originally known as Storage.NET, is a polycloud .NET cloud storage library to interface with multiple cloud providers from a single unified interface. Provides Blob storage (AWS S3, GCP, FTP, SFTP, Azure Blob/File/Event Hub/Data Lake) and Messaging (AWS SQS, Azure Queue/ServiceBus). Supports .NET 5+ and .NET Standard 2.0+. Pure C#. MIT license. Commercial use allowed.

FluentValidation by: Jeremy Skinner

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

FluentValidation.AspNetCore by: Jeremy Skinner

AspNetCore integration for FluentValidation

FluentValidation.DependencyInjectionExtensions by: Jeremy Skinner

Dependency injection extensions for FluentValidation

Fluid.Core by: Sebastien Ros

Fluid is a template engine based on the Liquid markup, with focus on performance and .NET programming patterns.