This community maintained list showcases .NET open source developer projects. It is intended to include projects that are useful for any aspect of the development process. For consumer projects, see the [.NET open source consumer projects list](dotnet-consumer-projects.md). PR a change into either list and it will be accepted (modulo duplicates).
Please sort projects alphabetically and provide a one-line description. GitHub/CodePlex (or other source) links are preferred, but feel free to also include marketing sites. Create new sections, as appropriate.
* [Fling OS](http://git.flingos.co.uk/fling-os/src) - [C# Operating System](http://www.flingos.co.uk/) designed for people to learn low-level development from.
* [Catel](https://github.com/catel/catel) - Application platform with IoC, logging, reflection and much more that serves as a base for applications that must be ready for future growth.
* [Enterprise Web Library (EWL)](https://github.com/enduracode/enterprise-web-library) - An extremely opinionated platform for web applications that trades off performance, scalability, and development flexibility for an ease of maintenance you won't find anywhere else. [Enterprise Web Library site](http://www.enterpriseweblibrary.org/).
* [KonfDB](https://github.com/punitganshani/konfdb) - Configuration Management as a Service for cross-platform, multi-tenant enterprise/hobby applications.
* [Akka.NET](http://github.com/akkadotnet) - Akka.NET is a toolkit and runtime for building highly concurrent, distributed, and fault tolerant event-driven applications on .NET & Mono. This community-driven port brings C# & F# developers the capabilities of the original Akka framework in Java/Scala. [[Project Site]](http://getakka.net/)
* [ClojureCLR](https://github.com/clojure/clojure-clr) - A .NET implemention of the [Clojure](http://clojure.org) programming language, built on the DLR.
* [Cobra](http://cobra-language.com/source/) - Clean, high-level syntax (Boo/Python-like). Static and dynamic binding. First class support for unit tests and contracts. Compiled performance with scripting conveniences. Lambdas and closures. Extensions and mixins
* [Dynamic Language Runtime](http://www.github.com/IronLanguages/main) - A toolkit for building dynamic languages for .NET.
* [Essence#](https://essencesharp.codeplex.com/) - Essence# is a fully dynamic and highly polymorphic programming language which features pervasive message passing, pervasive dynamic and strong typing, pervasive and deep reflection and pervasive object orientation.
* [IronPython](https://github.com/IronLanguages/main/tree/master/Languages/IronPython) - A .NET implementation of the [Python](https://www.python.org) programming language, built on the DLR. [IronPython Site](http://ironpython.net).
* [IronRuby](https://github.com/IronLanguages/main/tree/master/Languages/Ruby) - A .NET implementation of the [Ruby](https://www.ruby-lang.org) programming language, built on the DLR. [IronRuby Site](http://ironruby.net).
* [MoonSharp](https://github.com/xanathar/moonsharp/) - A Lua interpreter and remote debugger, written entirely in C#, easily embeddable in any application running on .NET 3.5+ and Mono.
* [Nemerle](https://github.com/rsdn/nemerle) - A high-level statically-typed programming language which offers functional, object-oriented and imperative features and has a simple C# like syntax and a powerful meta-programming system.
* [NiL.JS](https://github.com/nilproject/NiL.JS) - A .NET implementation of the ECMAScript language and runtime.
* [Phalanger](https://github.com/DEVSENSE/Phalanger) - full-featured PHP runtime & compiler for .NET/Mono frameworks. Phalanger is modern open-source implementation of PHP, compatible with the vast array of existing PHP code.
* [C# Coding Guidelines](http://csharpcodingguidelines.com) - A set of coding guidelines for C# 3.0, 4.0 and 5.0 that extend StyleCop and can be forked and adapted for internal use.
* [NemerleWeb](https://github.com/NemerleWeb/NemerleWeb) - Web MVVM library for .Net. It uses reactive data model which allows creating rich internet applications.
* [Albedo](https://github.com/ploeh/Albedo) - A .NET library targeted at making Reflection programming more consistent, using a common set of abstractions and utilities.
* [AngleSharp](https://github.com/FlorianRappl/AngleSharp) - Ultimate angle brackets parser library. It parses HTML5, MathML, SVG and CSS to construct a DOM based on the official W3C specification.
* [ArcGIS.PCL](https://github.com/davetimmins/ArcGIS.PCL) - Call ArcGIS Server REST API resources. You can also convert between ArcGIS features and GeoJSON.
* [Argument](https://github.com/ashmind/Argument) - Argument validation microframework that does one thing in the simplest way possible.
* [AshMind.Extensions](https://github.com/ashmind/ashmind-extensions) - A set of very conservative extension methods most of which closely follow naming and design patterns of .NET Base Class Library.
* [Brighter](https://github.com/iancooper/Paramore) - A Command Dispatcher and Command Processor library with support for Work or Task Queues over different MoM implementations such as RabbitMQ
* [Cimbalino Toolkit](https://github.com/Cimbalino/Cimbalino-Toolkit) - A set of useful and powerful tools that will help you build your Windows Platform applications.
* [ComparerExtensions](https://github.com/jehugaleahsa/comparerextensions) - Build IComparer and IEqualityComparer objects using natural language syntax.
* [DateTimeExtensions](https://github.com/kappy/DateTimeExtensions) - Common Date Time operations on the form of extensions to System.DateTime, including holidays and working days calculations on several culture locales.
* [DotNetOpenAuth](https://github.com/DotNetOpenAuth) - Library that adds support for your site visitors to login with their OpenIDs by just dropping an ASP.NET control onto your page.
* [FluentValidation](https://github.com/JeremySkinner/FluentValidation) - A small validation library for .NET that uses a fluent interface and lambda expressions for building validation rules.
* [Font-Awesome-WPF](https://github.com/charri/Font-Awesome-WPF) - WPF controls for the iconic font and CSS toolkit [Font Awesome](http://fortawesome.github.io/Font-Awesome/).
* [LINQ Extensions](https://github.com/TommasoScalici/LINQExtensions) - LINQ extensions for .NET is a collection of useful extensions methods that extends LINQ's capability. There are methods for combinatorics and sequence analysis, generation and manipulation.
* [LibGit2Sharp](https://github.com/libgit2/libgit2sharp) - C# language bindings for the [LibGit2](https://github.com/libgit2/libgit2) implementation of Git.
* [Math.NET Numerics](https://github.com/mathnet/mathnet-numerics) - Provides methods and algorithms for numerical computations in science, engineering and every day use.
* [Mathos Core Libary](http://mathos.codeplex.com/) - A library with algorithms for numerical calcultations in finance, statistics, pattern recognition, and more.
* [MoreLINQ](https://code.google.com/p/morelinq/) - LINQ to Objects is missing a few desirable features. This project will enhance LINQ to Objects with extra methods, in a manner which keeps to the spirit of LINQ.
* [Spartacus](https://github.com/wind39/spartacus) - Multi-purpose C# library, containing: 1) classes to access many types of databases in a fast, generic way; 2) classes to work with XLSX, CSV and DBF files; 3) PDF report engine.
* [Strongly Typed Client API Generators for ASP.NET Web API](https://webapiclientgen.codeplex.com/) - Strongly Typed Client API Generators generate strongly typed client API in TypeScript and C# codes supporting desktop, Universal Windows, Android and iOS.
* [Sweet.Jayson](https://github.com/ocdogan/Sweet.Jayson) - Fast, reliable, easy to use, fully json.org compliant, thread safe C# JSON library for server side and desktop operations.
* [WampSharp](https://github.com/Code-Sharp/WampSharp) - A C# implementation of [The Web Application Messaging Protocol](http://wamp.ws) - a protocol that provides messaging patterns of Remote Procedure Calls and Publish/Subscribe over WebSockets.
* [WebApiProxy](https://github.com/faniereynders/WebApiProxy) - An automatic proxy provider for RESTful services built on ASP.NET Web API. Includes JavaScript & C# client generation.
* [XamlEssentials](https://github.com/AdvancedREI/XamlEssentials) - Collection of helpers for Microsoft's XAML platforms.
* [Zlib.Portable](https://github.com/AdvancedREI/Zlib.Portable) - A Portable Class Library port of the Zlib library from http://dotnetzip.codeplex.com.
* [AForge.NET](http://www.aforgenet.com/) - a C# framework designed for developers and researchers in the fields of Computer Vision and Artificial Intelligence - image processing, neural networks, genetic algorithms, machine learning, robotics
* [Accord.NET Framework](https://github.com/accord-net/framework) - The Accord.NET Framework is a .NET machine learning framework combined with audio and image processing libraries completely written in C#.
* [DynamicImage](https://github.com/tgjones/dynamic-image) - WPF-based server-side image rendering system - lots of visual effects implemented as high-performance shaders. Has URL api, several plugins available.
* [OpenTK](https://github.com/opentk/opentk) - OpenTK is a low-level, cross-platform binding to OpenGL, OpenGL ES, OpenCL and OpenAL, available for Windows, Linux, Mac OS X, BSD, Android and iOS.
* [Exceptionless](https://github.com/exceptionless/Exceptionless) - Provides real-time .NET error reporting for your ASP.NET, Web API, WebForms, WPF, Console, and MVC apps. It organizes the gathered information into simple actionable data that will help your app become exceptionless!
* [ELMAH](https://github.com/elmah/Elmah) - [ELMAH (Error Logging Modules and Handlers)](https://elmah.github.io/) is an application-wide error logging facility that is completely pluggable. It can be dynamically added to a running ASP.NET web application, or even all ASP.NET web applications on a machine, without any need for re-compilation or re-deployment.
* [LogMaster4Net](https://github.com/kerryjiang/LogMaster4Net) - It is a central log server which can organize your logs in different applications in a same place but have same log behaviors (loggers, appenders, levels and rules) like in the indepedent applications before.
* [Caliburn Micro](https://github.com/Caliburn-Micro/Caliburn.Micro) - A small, yet powerful framework, designed for building applications across all XAML platforms.
* [Catel.MVVM](https://github.com/catel/catel) - Catel is an application development platform with the focus on MVVM.
* [MVVM Extensions](https://github.com/TommasoScalici/MVVMExtensions) - MVVM cross platform (.NET FW 4.5, WPF, Windows Runtime/Phone) extensions for .NET with support for async commands, MVVM-friendly Object and Task with support for UI notification.
* [Okra App Framework](https://github.com/OkraFramework/Okra.Core) - An MVVM framework for Windows Store applications including MVVM templates for Visual Studio.
* [Radical](https://github.com/RadicalFx/radical) - An infrastructure framework whose primary role is to help in the development of composite WPF/Silverlight/WP/WinRT applications based on the Model View ViewModel pattern.
* [ReactiveUI](https://github.com/reactiveui/ReactiveUI) - An MVVM framework that integrates with the Reactive Extensions for .NET to create elegant, testable User Interfaces that run on any mobile or desktop platform.
* [Simple Mvvm Toolkit](http://simplemvvmtoolkit.codeplex.com/) - Provides a simple framework and set of tools for getting up to speed quickly with applications based on the MVVM design pattern.
* [WPF Application Framework (WAF)](http://waf.codeplex.com) - A lightweight Framework that helps you to create well structured WPF Applications. It supports you in applying a Layered Architecture and the Model-View-ViewModel pattern.
* [API Port](https://github.com/microsoft/dotnet-apiport) - A tool that will analyze code for compatability issues when migrating between .NET Framework releases.
* [Crawler-Lib Build Tools](http://download.crawler-lib.net/BuildTools/) - [A PowerShell based toolbox](http://www.crawler-lib.net/build-tools) for automating the software build process, autmated testing and integration.
* [Glimpse](https://github.com/Glimpse/Glimpse) - Providing real time diagnostics & insights to the fingertips of hundreds of thousands of developers daily.
* [ILSpy](https://github.com/icsharpcode/ILSpy) - ILSpy is the open-source .NET assembly browser and decompiler.
* [Mini Profiler](https://github.com/MiniProfiler/dotnet) - A simple but effective mini-profiler for .NET.
* [Paket](https://github.com/fsprojects/Paket) - Dependency manager for .NET and Mono projects, which is designed to work well with NuGet packages and also enables referencing files directly from GitHub repositories.
* [Protobuf-net](https://code.google.com/p/protobuf-net/) - A .NET implementation of protobuf, allowing you to serialize your .NET objects efficiently and easily.
* [AutoFixture](https://github.com/AutoFixture/AutoFixture) - An open source framework for .NET designed to minimize the 'Arrange' phase of your unit tests. Its primary goal is to allow developers to focus on what is being tested rather than how to setup the test scenario, by making it easier to create object graphs containing test data.
* [FluentAssertions](http://www.fluentassertions.com/) - A very extensive set of extension methods that allow you to more naturally specify the expected outcome of unit tests and which make your assertions look beautiful, natural and most importantly, extremely readable.
* [SpecFlow](https://github.com/techtalk/specflow) - Cucumber clone for .NET for writing acceptance tests in natural langauge. [Site](http://www.specflow.org/)
* [TestStack.FluentMvcTesting](https://github.com/TestStack/TestStack.FluentMVCTesting) - Simple, terse, fluent unit testing for ASP.NET MVC Controllers.
* [TestStack.Seleno](https://github.com/TestStack/TestStack.Seleno) - Seleno helps you write automated UI tests in the right way by implementing Page Objects and Page Components and by reading from and writing to web pages using strongly typed view models.
* [TestStack.White](https://github.com/TestStack/White) - White is a framework for automating rich client applications based on Win32, WinForms, WPF, Silverlight and SWT (Java) platforms.
* [Autofac](https://github.com/autofac/Autofac) - Autofac is an addictive Inversion of Control container for .NET 4.5, Silverlight 5, Windows Store apps, and Windows Phone 8 apps.
* [Castle Windsor](https://github.com/castleproject/Windsor) - A mature Inversion of Control container available for .NET and Silverlight
* [DI Feature Tests](https://github.com/ashmind/net-feature-tests) - Tests that track commmon DI features among multiple containers
* [DryIoc](https://bitbucket.org/dadhi/dryioc) - DryIoc is small, fast, capable IoC Container for .NET
* [fFastInjector](https://ffastinjector.codeplex.com/) - fFastInjector is a high-performing dependency injector, service locator, and/or IOC (inversion of control) container.
* [HaveBox](https://bitbucket.org/Have/havebox/wiki/Home) - HaveBox is a very fast and lightweight IoC containter. The goal is to keep it fast and light, and at the same time easy to use.
* [Hiro](https://github.com/philiplaureano/Hiro) - An ultra-lightweight, inversion of control container compiler framework
* [IfInjector](https://github.com/iamahern/IfInjector) - High performance mobile micro-IoC container.
* [LightCore](https://peterbucher.kilnhg.com/Code/LightCore/Group/Default?nr=) - [A lightweight dependency injection container](http://lightcore.ch/en/default.aspx) that can be used as a service locator and despite its simplicity and ease boasts numerous features.
* [LightInject](https://github.com/seesharper/LightInject) - A ultra lightweight IoC container
* [MicroSliver](https://microsliver.codeplex.com/) - MicroSliver is a micro, non-bloat, non-intimidating and speedy .NET (ASP.NET, Silverlight, RIA Services, WPF, Forms and Metro!)
* [Mugen Injection](http://mugeninjection.codeplex.com/) - The MugeniInjection is a lightweight and fast managed IoC (Inversion of Control) and DI (Dependency Injection) with support for constructor, property and method call injection
* [QuickInject](https://github.com/isabgol/QuickInject) - QuickInject is a Unity 3.5 based IoC container that aims to give the Unity container a performance advantage in basic scenarios.
* [Simple Injector](https://github.com/simpleinjector/SimpleInjector/) - Simple Injector is an easy-to-use Dependency Injection library for .NET 4+ that supports Silverlight 4+, Windows Phone 8, Windows 8 including Universal apps and Mono.
* [Spring.NET](https://github.com/spring-projects/spring-net) - Spring.NET is an open source application framework that makes building enterprise .NET applications easier.
* [StructureMap](https://github.com/structuremap/structuremap) - StructureMap is a Dependency Injection / Inversion of Control tool for .Net that can be used to improve the architectural qualities of an object oriented system by reducing the mechanical costs of good design techniques.
* [StyleMVVM](https://stylemvvm.codeplex.com/) - Style MVVM is a toolkit designed for the Windows Store platform around the idea of being light weight and fast.
* [TinyIoC](https://github.com/grumpydev/TinyIoC) - An easy to use, hassle free, Inversion of Control Container for small projects, libraries and beginners alike.
* [Unity Container](http://unity.codeplex.com/) - The Unity Container (Unity) is a lightweight, extensible dependency injection container with optional support for instance and type interception.
* [Dapper](https://github.com/StackExchange/dapper-dot-net) - Dapper is a single file you can drop in to your project that will extend your IDbConnection interface.
* [Eggado](https://bitbucket.org/raboof/eggado) - Eggado takes generics, lambdas, expression trees, dynamic methods and DLR and uses them to breathe new life into data access using good old ADO.NET. It's for folks who can live with a SQL dialect.
* [linq2db](https://github.com/linq2db/linq2db/) - Lightweight ORM and LINQ provider with support for various databases including MS SQL, PostgreSQL, Oracle and MySQL
* [NMEA Parser](https://github.com/dotMorten/NmeaParser) - Library for handling NMEA message in Windows Desktop, Store, Phone and Xamarin (Android + iOS), coming from files, Bluetooth, serial port or any stream.
* [SQL LocalDB Wrapper](https://github.com/martincostello/sqllocaldb) - SQL LocalDB Wrapper is an assembly providing interop with the SQL LocalDB native API from managed code using .NET APIs.
* [LINQ2DynamoDB](https://github.com/scale-tone/linq2dynamodb) - A type-safe data context for AWS DynamoDB with LINQ, in-memory caching and OData support.
* [Elephant](https://github.com/takenet/elephant) - Persistence library that provides common data structures as composable elements to abstract any storage engine, including (No)SQL databases.
* [MahApps.Metro](https://github.com/MahApps/MahApps.Metro) - A toolkit for creating Metro / Modern UI styled WPF apps. [mahapps.com](http://mahapps.com)
* [Material Design in XAML Toolkit](https://github.com/ButchersBoy/MaterialDesignInXamlToolkit) - WPF/XAML resources, styles & templates for creating applications using Material Design
* [Hangfire](https://github.com/HangfireIO/Hangfire) - An easy way to perform fire-and-forget, delayed and recurring tasks inside ASP.NET applications.
* [Quartz.Net](https://github.com/quartznet/quartznet) - A full-featured, open source job scheduling system that can be used from smallest apps to large scale enterprise systems.
* [FluentScheduler](https://github.com/fluentscheduler/FluentScheduler) - Task scheduler with fluent interface that runs automated tasks (cron jobs) from your application.
* [RoundHouse](https://github.com/chucknorris/roundhouse) - RoundhousE is a Database Migration Utility for .NET using sql files and versioning based on source control
* [Warewolf Easy Service Bus](https://github.com/Warewolf-ESB/Warewolf-ESB) - An open source easy to use service bus, built on numerous .Net technologies including WF (Windows Workflow Foundation), SignalR and WPF.
* [CacheManager](https://github.com/MichaCo/CacheManager) - A configurable abstraction layer for caching. It supports various caches, like redis and memcached, and provides many advanced features, like layered cache, synchronization, serialization etc.
* [Orleans](https://github.com/dotnet/orleans) - Framework that provides a straight-forward approach to building distributed high-scale computing applications using virtual actor model.
* [AlexaSkillsKit.NET](https://github.com/AreYouFreeBusy/AlexaSkillsKit.NET) - .NET library to write Alexa Skills that's interface-compatible with Amazon's AlexaSkillsKit for Java and matches that functionality.
This list is just a starting point - also take a look at all the projects on [CodePlex](http://www.codeplex.com/) and on [GitHub Trending C#](https://github.com/trending?l=csharp).
[@quozd](http://twitter.com/quozd "@quozd on Twitter") hosts an [Awesome .NET!](https://github.com/quozd/awesome-dotnet) list. Also worth checking out.
