Si on jetait un coup d'oeil sur la liste des projets OpenSource en C# ( bon vu le nombre, on va se limiter à sourceForge.net ).
Liste des projets C# sur SourceForge.net

Quelques morceaux de choix ( je me suis arrêter à la page 10, il y en avait bcp trop, je vous invite donc à aller faire un tour ).

• 6. Netron - Generic diagramming, graph-drawing and graph-layout kit for the Microsoft .Net framework
• 8. SharpDevelop - SharpDevelop is an open source IDE for the .NET platform. It is entirely written in C#, and supports various project types in multiple programming languages
• 17. NASA World Wind - NASA World Wind is a graphically rich 3D virtual globe for use on desktop computers running Windows. It combines NASA imagery generated from satellites that have produced the Blue Marble, Landsat 7, SRTM, MODIS and more.
• 21. Ajax.NET Library - The Ajax.NET Library is an implementation of AJAX (Asynchronous JavaScript and XML) for the Microsoft .NET Framework. AJAX is used by Google Maps, Google Mail, Flickr,... This library will export methods to use it directly on the client-side JavaScript
• 25. NxBRE - NxBRE is a lightweight Business Rule Engine (aka Rule Based Engine) for the .NET platform, composed of a forward-chaining inference engine and an XML-driven flow control engine. It supports RuleML 0.86 Naf Datalog and Visio 2003 modeling.
• 26. RSS Bandit - A desktop news aggregator written in C#.
• 46. QueryCommander - Sql editor, simular to the Microsoft Query Analyzer, in a Visual Studio type of enviroment. QueryCommander includes features like IntelliSense, automatic comment header, xml-documentation, xml2data etc. 100% of all donations go to Plan International
• 57. NHibernate - A .NET port of the excellent Java Hibernate (http://www.hibernate.org/) relational persistence tool.
• 60. dotLucene a search engine library - dotLucene is the .NET implementation of the Lucene full-text search engine library
• 66. Simple Rule Engine - SRE (Simple Rule Engine) is a lightweight forward chaining inference rule engine for .NET. Its 'simple' because of the simplicity in writing and understanding the rules written in XML, but this 'simple' engine can solve complex problems.
• 141. NDoc - NDoc is an extensible code documentation generation tool for .NET developers.
• 158. GPSProxy - GPSProxy is a .NET Compact Framework application that copies GPS data from one COM port on a Pocket PC to another, optionally translating the GPS data format from NMEA 0183 to the Garmin GPS protocol.
• 185. XUL# - XUL# is a c# library for writing web and stand-alone application with Mozilla XUL user interface. The same application can be hosted into ASP.NET or Windows.Form (or Mono) Language: C#, XUL, HTML
• 204. MCMS CustomPropertyDbEx - An alternate solution to MCMS Custom Properties: CustomPropertyDbEx moves all custom properties to a seperate database permitting custom properties for all CMS assets: channels, postings, template galleries, templates, resource galleries, resources, etc.
• 212. FlexWiki - FlexWiki is a collaborative web-based authoring environment implemented on the Microsoft .NET platform.

PMA : (Petit mot de l'auteur ) Parmi tous ces projets, j'en ai utilisé ou tester un certain nombre celui qui m'avait bcp marqué est le moteur de règle NxBre, je devais etudier les moteurs de règle sous .net à l'époque j'avais sélectionné :
- Yasu
- NxBre
- BlazeAdvizor de Fair Isaac
- IRule
( Je n'avais retenu que ces quatres, car le temps imparti pour rendre mon rapport etait de 3 jours en prenant en compte la demi journee de formation que j'ai eu avec quelqu'un de Fair Isaac. )

Par rapport à mes besoins mon choix se portait bcp plus sur IRule et BlazeAdvizor, mais j'ai pu parcourir le source de NxBre, tout comme Yasu je dois dire que le code est d'un bon niveau.