GDC 2006: XNA Announcements
https://www.microsoft.com/xna/
XNA Framework Simplifies Cross-Platform Game Development - "The XNA Framework contains a custom implementation of the Microsoft® .NET Framework and new game-development-specific libraries designed to help game developers more easily create cross-platform games on Windows® and Xbox 360 using the highly productive C# programming language. Using the XNA Framework, game developers will benefit from the ability to re-use code and game assets in developing multiplatform titles, without sacrificing performance or flexibility."
Also, you can download the XNA Build March 2006 CTP here.