Frameworks, Libraries and Tools

API

• Flurl - Fluent URL builder and testable HTTP for .NET https://flurl.dev.
• WebAnchor - Web Anchor provides type-safe, testable and flexible, runtime-generated access to web resources.
• refit - The automatic type-safe REST library for Xamarin and .NET.
• Hot Chocolate - GraphQL server for .Net Core and .NET Framework.

Application Frameworks

• ASP.NET Boilerplate - ASP.NET Boilerplate is a general purpose application framework especially designed for new modern web applications. It uses already familiar tools and implements best practices around them to provide you a SOLID development experience.
• Abp vNext - Abp vNext is the next generation of the open source ASP.NET Boilerplate framework. It's a complete architecture and strong infrastructure to create modern web applications!
• AsyncEx - A helper library for async/await.
• akka.net - Toolkit and runtime for building highly concurrent, distributed, and fault tolerant event-driven applications on .NET & Mono.
• CQRSlite - Lightweight framework for helping writing CQRS and Eventsourcing applications in C#.
• dotvvm - Open source MVVM framework for Web Apps.
• EventFlow - Async/await first CQRS+ES and DDD framework for .NET.
• MassTransit - Distributed Application Framework for .NET.
• Nancy - Lightweight, low-ceremony, framework for building HTTP based services on .NET and Mono.
• Prism - Prism is a framework for building loosely coupled, maintainable, and testable XAML applications in WPF, Windows 10 UWP, and Xamarin Forms.
• ServiceStack - Thoughtfully architected, obscenely fast, thoroughly enjoyable web services for all https://servicestack.net.
• MagicOnion - gRPC based HTTP/2 RPC Streaming Framework for .NET, .NET Core and Unity.
• Chromely - Lightweight Alternative to Electron.NET, Electron for .NET/.NET Core.

Application Templates

• .NET Boxed - Project templates with batteries included, providing the minimum amount of code required to get you going. Includes ASP.NET Core API and GraphQL Templates.
• EISK - Provides developer resources with simple use cases to build scalable applications on top of .NET Core with architectural best practices (DDD, onion architecture etc)
• Toucan - Boilerplate for building single page apps. Server is multi-project .Net Core solution designed around SOLID principles. Client is TypeScript 2, Vuejs 2, Vuex 2.
• Serenity - Serenity is an ASP.NET MVC / TypeScript application platform designed to simplify and shorten development of data-centric business applications with a service based architecture.

Authentication and Authorization

• stuntman - Library for impersonating users during development leveraging ASP.NET Identity.

Build Automation

• cake-build - Cross platform build automation system.
• FlubuCore - A cross platform build and deployment automation system for building projects and executing deployment scripts using C# code.

Caching

• CacheManager - Open source caching abstraction layer for .NET written in C#. It supports various cache providers and implements many advanced features. http://cachemanager.michaco.net
• Stack Exchange Redis - High performance general purpose redis client for .NET languages (C# etc).

CMS

• NetCoreCMS - An Open source ASP.NET Core 2.0 CMS. It currently supports MySQL and planned to implement MSSQL, SQLite and PostgreSQL. Also it is a modular CMS supports theme, skin, custom layout, widgets, multiple language (En, BN).
• Orchard Core CMS - Open Source Content Management System built with ASP.NET Core on top of a Modular and Extensible Application Framework.

Code Analysis and Metrics

• BenchmarkDotNet - Powerful .NET library for benchmarking.

Compilers, Transpilers and Languages

• Mond - A dynamically typed scripting language written in C# with a REPL, debugger, and simple embedding API.

Compression

• sharpcompress - Fully managed C# library to deal with many compression types and formats.

Cryptography

• BCrypt.Net - Bringing updates to the original bcrypt package.

Database

• DBreeze - C# .NET MONO NOSQL (key value store embedded) ACID multi-paradigm database management system.
• JsonFlatFileDataStore - Simple JSON flat file data store with support for typed and dynamic data.

Database Drivers

• confluent-kafka-dotnet - Confluent's Apache Kafka .NET client.
• npgsql - .NET data provider for PostgreSQL. It allows any program developed for .NET framework to access a PostgreSQL database server. It is implemented in 100% C# code. PostgreSQL versions since 9.1 are officially supported, others may work. http://www.npgsql.org
• RethinkDb.Driver - C#/.NET RethinkDB driver with 100% ReQL API coverage.

Date and Time

• Exceptionless.DateTimeExtensions - DateTimeRange, Business Day and various DateTime, DateTimeOffset, TimeSpan extension methods.

Distributed Computing

• Foundatio - Pluggable foundation blocks for building distributed apps

E-Commerce and Payments

• Stripe - Typed .NET clients for stripe.com REST APIs.

Exceptions

• Exceptionless - Exceptionless .NET Client

Functional Programming

• language-ext - C# functional language extensions and 'Erlang like' concurrency system.

Graphics

• GLFWDotNet - .NET bindings for GLFW.
• ImageProcessor - A fluent wrapper around System.Drawing for the processing of image files http://imageprocessor.org. 4.5.x or above
• ImageSharp - Cross-platform library for processing of image files written in C#.
• QRCoder - A pure C# Open Source QR Code implementation.
• SharpBgfx - C# bindings for the bgfx graphics library.

GUI

• Avalonia - A multi-platform .NET UI framework (formerly known as Perspex).

IDE

• Mono - MonoDevelop enables developers to quickly write desktop and web applications on Linux, Windows and Mac OS X. It also makes it easy for developers to port .NET applications created with Visual Studio to Linux and Mac OS X maintaining a single code base for all platforms.

IOC

• Autofac - Addictive .NET IoC container.
• Grace - Grace is a feature rich Dependency Injection Container designed with ease of use and performance in mind.
• SimpleInjector - Easy, flexible, and fast Dependency Injection library that promotes best practice to steer developers towards the pit of success.

Logging

• NLog - Advanced .NET, Silverlight and Xamarin Logging with support for structured and non structured logging.
• Q42.Logging.ApplicationInsights - Log appender for the build in ASP.NET Core logging to send all logs to Application Insights.
• Serilog.Exceptions - Serilog.Exceptions is an add-on to Serilog to log exception details and custom properties that are not output in Exception.ToString().

Machine Learning and Data Science

• Accord - Machine learning, computer vision, statistics and general scientific computing for .NET.
• TensorFlowSharp - TensorFlow API for .NET languages.

Mail

• FluentEmail - All in one email sender for .NET and .NET Core
• MailKit - Cross-platform .NET library for IMAP, POP3, and SMTP.
• MimeKit - Cross-platform .NET MIME creation and parser library with support for S/MIME, PGP, DKIM, TNEF and Unix mbox spools.
• netDumbster - a .Net Fake SMTP Server used for testing. Clone of the popular Dumbster.

Misc

• AngleSharp - The ultimate angle brackets parser library. It parses HTML5, MathML, SVG and CSS to construct a DOM based on the official W3C specification. Comparable to beautifulsoup4 of python.
• httpclient-interception - .NET Standard library for intercepting server-side HTTP dependencies.
• Guard - A high-performance, extensible argument validation library.

ORM

• Chloe - A lightweight and high-performance Object/Relational Mapping(ORM) library for .NET.
• Dapper-FluentMap - Provides a simple API to fluently map POCO properties to database columns when using Dapper.
• nhibernate-core - NHibernate Object Relational Mapper.
• NPoco - Simple microORM that maps the results of a query onto a POCO object. Project based on Schotime's branch of PetaPoco.
• ServiceStack.OrmLite - Light, simple and fast convention-based POCO ORM.
• SQLStreamStore - Stream Store library targeting SQL based implementations for .NET.

Query Builders

• SqlKata - Elegant Sql Query Builder, that supports complex queries, joins, sub queries, nested where conditions, vendor engine targets and more

Queue and Messaging

• rabbitmq-dotnet-client - RabbitMQ .NET client https://www.rabbitmq.com.
• Rebus - Simple and lean service bus implementation for .NET.
• NServiceBus - NServiceBus is part of the Particular Service Platform, which contains tools to build, monitor, and debug distributed systems.

Scheduler and Job

• LiquidState - Efficient asynchronous and synchronous state machines for .NET.

SDKs

• firebase-admin-dotnet - Firebase Admin .NET SDK
• octokit.net - GitHub API client library for .NET.
• SendGrid-csharp - C# client library for using the full SendGrid API.
• statsd-csharp-client - .NET Standard compatible C# client to interface with Etsy's excellent statsd server.

Searching

• Algolia.Search - Repository for the official Algolia .NET client.
• Elasticsearch.Net & NEST - Repository for both NEST and Elasticsearch.NET, the two official elasticsearch .NET clients.

Security

• Jwt.Net - Jwt.Net, a JWT (JSON Web Token) implementation for .NET.

Serialization

• msgpack-cli - MessagePack implementation for Common Language Infrastructure / msgpack.org.
• Newtonsoft.Json - Popular high-performance JSON framework for .NET.
• Schema.NET - Schema.org objects turned into strongly typed C# POCO classes for use in .NET. All classes can be serialized into JSON/JSON-LD and XML, typically used to represent structured data in the head section of html page.
• ServiceStack.Text - JSON, JSV and CSV Text Serializers.
• ZeroFormatter - Fast binary (de)serializer for .NET.

Testing

• Bogus - Simple and sane fake data generator for C#. Based on and ported from the famed faker.js.
• FluentAssertions - Set of .NET extension methods that allow you to more naturally specify the expected outcome of a TDD or BDD-style test.
• NSubstitute - A friendly substitute for .NET mocking frameworks.
• xUnit.net - A free, open source, community-focused unit testing tool for the .NET Framework.

Tools

• mRemoteNG - The next generation of mRemote, open source, tabbed, multi-protocol, remote connections manager

Web Socket

• Fleck - Fleck is a WebSocket server implementation in C#. Fleck requires no inheritance, container, or additional references.
• WampSharp - C# implementation of The Web Application Messaging Protocol - Protocol that provides messaging patterns of Remote Procedure Calls and Publish/Subscribe over WebSockets.

Sample Projects

Workflow

• allReady - Open-source solution focused on increasing awareness, efficiency and impact of preparedness campaigns as they are delivered by humanitarian and disaster response organizations in local communities. http://www.htbox.org/projects/allready

Starter Kits

Workflow

• react-aspnet-boilerplate - Starting point for building isomorphic React applications with ASP.NET Core 1, leveraging existing techniques.