Developers can view and debug Microsoft source code.
Microsoft is offering a read-only version of the source code for .Net Framework libraries to developers who upgrade to Visual Studio 2008.
Software projects include The .Net Base Class Libraries, ASP.Net (including System.Web.Extensions), Windows Forms, Windows Presentation Foundation, ADO.Net and XML.
"Enabling source code access and debugger integration of the .Net Framework libraries is going to be really valuable for .Net developers," said Scott Guthrie, general manager of the Microsoft developer division, on a company blog.
"Being able to step through and review the source should provide much better insight into how the .Net Framework libraries are implemented, and in turn enable users to build better applications and make even better use of them."
Microsoft is planning to add further framework libraries, including Language Integrated Query and Windows Communication Foundation, in due course.
Developers wishing to participate can find code access details for .Net source code in a blog kept by Shawn Burke, a director in the Microsoft developer division.