DotNetNuke is a web content management system based on Microsoft .NET. The Community Edition is open source.
DotNetNuke is a program that runs on Microsoft ASP.NET. It is also a framework, meaning, it is a program that is designed to be extended. One of the ways you extend the framework is to create modules. These modules are installed inside a DotNetNuke installation and when they run in that DotNetNuke installation they extend the framework to create a DotNetNuke website also called a portal.
Features
1)A rich-text editor
2)File management
3)Cloud-ready with MS Azure compatibility
4)Mobile API and basic mobile device detection
5)Core written in C#
6)Single installation, multiple portals
7)Social API (in DNN 6.2 and above)
8)Modern client-side Web tools like CSS 3, HTML 5 and JQuery
9)Bulk email
10)Robust security
11)Administration features like: security roles, protected content and site log