- Ajax Control Toolkit – Microsoft
- AJAXNet Pro
- ASP.NET MVC Project Awesome – a rich set of helpers (controls) that you can use to build highly responsive and interactive Ajax-enabled Web applications. These helpers include Autocomplete, AjaxDropdown, Lookup, Confirm Dialog, Popup Form and Pager. Thanks Omu (April 20, 2011)
- Prebuild – Generate project files for all VS version, including major IDE’s and tools like SharpDevelop, MonoDevelop, NAnt and Autotools
- Genuilder – Precompiler which lets you transform your source code during the build. Thanks Harry McIntyre (April 13, 2011)
- Microsoft Chart Controls for ASP.NET 3.5 SP1
- Microsoft Chart Controls for Winforms
- ZedGraph Charting
- NPlot – Charting for ASP.NET and WinForms
- Graph# – a graph layout framework contains some layout algorithms and a GraphLayout control for WPF applications. Thanks Florian Standhartinger(April 20, 2011)
- PowerCollections – is a library that provides generic collection classes that are not available in the .NET framework. Some of the collections included are the Deque, MultiDictionary, Bag, OrderedBag, OrderedDictionary, Set, OrderedSet, and OrderedMultiDictionary. Thanks Adam Ralph (April 20, 2011)
- YUI Compressor (CSS and JS minification)
- AjaxMinifier (in other downloads) (CSS and JS minification. Also includes MSBuild task)
- SevenZipSharp to pack, unpack a lot of different packages (including RAR, 7ZIP, etc).
- ZipStorer A Pure C# Class to Store Files in Zip
- Krypton – Free winform controls. Link fixed (April 14, 2011)
- Source Grid – A Grid control
- DevExpress – Over 60 Free Controls from DevExpress. Thanks Florian Standhartinger (April 20, 2011)
- ObjectListView – is a C# wrapper around a .NET ListView. It makes the ListView much easier to use and provides some neat extra functionality. Thanks Florian Standhartinger (April 20, 2011)
- Mapper Extensions Thanks giometrix (April 14, 2011)
- Data accessors from the Data Access Application Block
- Value Injecter – ets you define your own convention-based matching algorithms (ValueInjections) in order to match up (inject) source values to destination values. Thanks Omu (April 20, 2011)
Dependency Injection/Inversion of Control
- Unity Framework – Microsoft
- StructureMap – Jeremy Miller
- Castle Windsor
- Spring Framework
- Simple Service Locator
- Managed Extensibility Framework
- Funq – a high performance DI framework by eliminating all runtime reflection through the use of lambdas and generic functions as factories. Thanks Marcel Popescu (April 20, 2011).
- Munq – a very small, fast dependency injection container designed for ASP.NET applications, both Webforms and MVC. It has, by design, limited features. The main goal has been to minimize the CPU required for Resolving types from the container. Thanks Marcel Popescu (April 20, 2011).
Design by Contract
- SharpDevelop – is a free IDE for C#, VB.NET and Boo projects. Thanks Florian Standhartinger (April 20, 2011).
- Logging Application Block – Microsoft
- Log4Net – Apache
- Error Logging Modules and Handlers(ELMAH)
- Logging Abstraction Api “Common.Logging”
- NHibernate and FluentNHibernate
- Castle ActiveRecord
- Truss Data binding and real time property sync library
Automated Web Testing
Misc Testing/Qualitysupport/Behavoir Driven Development (BDD)
MS Word/Excel Documents Manipulation
- DocX to create, read, manipulate formatted word documents. Easy syntax, working nicely, actively developed. No Microsoft Office necessary.
- Excel XML Writer allows creation of .XLS (Excel) files. No Microsoft Office necessary. Been a while since it has been updated. It also provides code generator to create code from already created XLS file (saved as xml). Haven’t tested this but looks very promising. Too bad author is long time gone.
- Excel Reader allows creation/reading of .XLS (Excel) files. No Microsoft Office necessary. Been a while since it has been updated.
- Excel Package allows creation/reading of .XLSX (Excel 2007) files. No Microsoft Office necessary. Author is gone so it’s out of date.
- EPPlus is based on Excel Package and allows creation/reading of .XLSX (Excel 2007). It is actually the most advanced even comparing to NPOI.
- NPOI is the .NET version of POI Java project at http://poi.apache.org/. POI is an open source project which can help you read/write xls, doc, ppt files.
- sharp2word – a Word 2003 XML Documents Generator from C# code without any components or libraries. Thanks dublicator (April 20, 2011)
- ClosedXML – an actively developed library for generating OpenXML Excel files. Thanks Joseph Robichaud (April 26, 2011)
- sharpserializer – xml/binary serializer for wpf, asp.net and silverlight
- Protobuf.NET – fastest serialization port protobuf format into .NET platform. Thanks slava pocheptsov (April 26, 2011)
- LinqToTwitter – Linq-based wrapper for all Twitter API functionality in C#
- Facebook C# SDK – A toolkit for creating facebook applications / integrating websites with Facebook using the new Graph API or the old rest API.
Package managers for external libraries
- NuGet (formerly known as NuPack) – Microsoft (developer-focused package management system for the .NET platform intent on simplifying the process of incorporating third party libraries into a .NET application during development)
- OpenWrap – Sebastien Lambla – Open Source Dependency Manager for .net applications
- Rhino Mocks
- fakeiteasy – a .Net dynamic fake framework for creating all types of fake objects, mocks, stubs etc. Thanks Omu (April 20, 2011)
- NSubstitute – a A friendly substitute for .NET mocking frameworks. Thanksxerxesb (May 10, 2011)
- Shouldly – How asserting should be. Thanks xerxesb (May 10, 2011)
- Smart Thread Pool – Thread Pool management library
- Retlang – a high performance C# threading library. Thanks MarcBot (April 13, 2011)
- bbv.Common – an open source library of software components that makes building multi-threaded, event-based and loosely coupled systems easy. Thanks Urs Enzler (April 14, 2011)
- PowerThreading – a llibrary (DLL) containing many classes to help with threading and asynchronous programming. Thanks Adam Ralph (April 20, 2011)
- CSLA Framework – Business Objects Framework
- AForge.net – AI, computer vision, genetic algorithms, machine learning
- Prism – Composit UI application block for WPF, Silverlight and WP7 – Microsoft patterns & practices
- Enterprise Library 5.0 – Logging, Exception Management, Caching, Cryptography, Data Access, Validation, Security, Policy Injection – Microsoft patterns & practices
- File helpers library
- C5 Collections – Collections for .NET
- Quartz.NET – Enterprise Job Scheduler for .NET Platform
- MiscUtil – Utilities by Jon Skeet
- Noda Time – DateTime replacement (idomatic port of Joda Time from Java)
- Lucene.net – Text indexing and searching
- Json.NET – Linq over JSON
- Flee – expression evaluator
- PostSharp – AOP
- IKVM – brings the extensive world of Java libraries to .NET.
- C# Webserver – Embeddable webserver
- Long Path – Microsoft
- .NET Engines for the GOLD Parsing System
- NCQRS – library for event-driven architectures (CQRS).
- Reactive Extensions for .NET – a library for composing asynchronous and event-based programs using observable collections. Thanks steve (April 14, 2011)
- Mono.GameMath – a project to develop a highly-performant math library for games, based on XNA APIs. Thanks Alex Rønne Petersen (April 14, 2011)
- SLSharp – a runtime IL-to-GLSL translation engine, allowing people to write GLSL shaders as C# code. Thanks Alex Rønne Petersen (April 14, 2011)
- InfusionSoftDotNet – a dll to ease the pain for .Net developers to access the InfusionSoft API. Thanks Michael Gibbs (April 20, 2011)
- re-mix – provides mixins for C# and Visual Basic .NET. Thanks Stefan Papp(April 20, 2011)
- Mono.Cecil – a library written by Jb Evain to generate and inspect programs and libraries in the ECMA CIL format. It has full support for generics, and support some debugging symbol format. Thanks Florian Standhartinger(April 20, 2011)
- ImapX – is an modern .NET 2.0 library for management of IMAP folders, supports SSL Connection and different IMAP formats, such as Gmail IMAP, AOL IMAP (November 30, 2011)