Castle.Core by: Castle Project Contributors

Castle Core, including DynamicProxy, Logging Abstractions and DictionaryAdapter

CommandLineParser by: Giacomo Stelluti Scala

Terse syntax C# command line parser for .NET with F# support. The Command Line Parser Library offers to CLR applications a clean and concise API for manipulating command line arguments and related tasks.

Confluent.Kafka by: Confluent Inc., Andreas Heider

Confluent's .NET Client for Apache Kafka

ConsoleAppFramework by: Cysharp

Zero Dependency, Zero Overhead, Zero Reflection, Zero Allocation, AOT Safe CLI Framework powered by C# Source Generator.

CsQuery by: James Treworgy

CsQuery is an HTML parser, CSS selector engine and jQuery port for .NET 4 and C#. It implements all CSS2 and CSS3 selectors, all the DOM manipulation methods of jQuery, and some of the utility methods.

CsvHelper by: Josh Close

A library for reading and writing CSV files. Extremely fast, flexible, and easy to use. Supports reading and writing of custom class objects.

Cucumber.Messages by: Cucumber Ltd, TechTalk

Protocol Buffer messages for Cucumber's and SpecFlow's inter-process communication

Dapper by: Sam Saffron, Marc Gravell, Nick Craver

A high performance Micro-ORM supporting SQL Server, MySQL, Sqlite, SqlCE, Firebird etc..

DocumentFormat.OpenXml by: Microsoft

The Open XML SDK provides tools for working with Office Word, Excel, and PowerPoint documents. It supports scenarios such as: - High-performance generation of word-processing documents, spreadsheets, and presentations. - Populating content in Word files from an XML data source. - Splitting up (shredding) a Word or PowerPoint file into multiple files, and combining multiple Word/PowerPoint files into a single file. - Extraction of data from Excel documents. - Searching and replacing content in Word/PowerPoint using regular expressions. - Updating cached data and embedded spreadsheets for charts in Word/PowerPoint. - Document modification, such as removing tracked revisions or removing unacceptable content from documents.

DotLiquid by: Tim Jones, Alessandro Petrelli

DotLiquid is a templating system ported to the .NET framework from Ruby’s Liquid Markup.

EntityFramework by: Microsoft

Entity Framework is Microsoft's recommended data access technology for new applications.

Enums.NET by: Tyler Brinkley

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

EPPlus by: EPPlus Software AB

A spreadsheet library for .NET framework and .NET core

Fable by: Alfonso García-Caro Núñez

F# to JS compiler

FastEndpoints by: FastEndpoints

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

FastExpressionCompiler.src by: Maksim Volkau

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

FluentAssertions by: Dennis Doomen

A very extensive set of extension methods that allow you to more naturally specify the expected outcome of a TDD or BDD-style unit test. Runs on 4.0 and 4.5 (Desktop and Windows Store), CoreCLR, Silverlight 5 and Windows Phone 8, 8.1 and 8.1 for Silverlight. Supports the unit test frameworks MSTest, MSTest2, NUnit, XUnit, XUnit2, MBUnit, Gallio, MSpec, and NSpec.

FluentValidation by: Jeremy Skinner

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

Gherkin by: Cucumber Ltd, Gaspar Nagy

Cross-platform parser for the Gherkin language, used by Cucumber, SpecFlow and other Cucumber-based tools to parse feature files.

Google.Protobuf by: Google Inc.

C# runtime library for Protocol Buffers - Google's data interchange format.