First Source Code for .NET Framework Libraries Released

Microsoft releases .NET 3.5 Framework library source code.

Microsoft has followed up on its promise to release the .NET 3.5 Framework library source code.

Libraries Now Open

A list of what's available for developers to view:
  • .NET Base Class Libraries (including System, System.CodeDom, System.Collections, System.ComponentModel, System.Diagnostics, System.Drawing, System.Globalization, System.IO, System.Net, System.Reflection, System.Runtime, System.Security, System.Text, System.Threading, etc.)
  • .ASP.NET (System.Web, System.Web.Extensions)
  • Windows Forms (System.Windows.Forms)
  • Windows Presentation Foundation (System.Windows)
  • ADO.NET and XML (System.Data and System.Xml)
Source: Microsoft
The company released the source code of more than a dozen libraries -- including ASP.NET, Windows Presentation Layer, Windows Forms and the .NET Base Class Libraries -- last month (see "Libraries Now Open").

Scott Guthrie, general manager of the Microsoft Developer Division, is promising that more libraries will come soon, including ones for Workflow, Windows Communication Foundation and LINQ.

"We think that enabling source code access and debugger integration of the .NET Framework libraries is going to be really valuable for .NET developers," he says in his blog post announcing the release of the class libraries. "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 you to build better applications and make even better use of them."

His blog includes instructions for configuring Visual Studio 2008 to access and debug the source code.

While the source code is being released under the company's read-only reference license (as originally planned), Guthrie notes Microsoft has made a change to the license terms.

"When we announced that we were releasing the source code back in October, some people had concerns about the potential impact of their viewing the source," notes Guthrie. Now, if a developer is coding for the Windows platforms, "You can look at the code, even if that software has 'the same or substantially the same features or functionality' as the .NET Framework," he says.

About the Author

Becky Nagel is the vice president of Web & Digital Strategy for 1105's Converge360 Group, where she oversees the front-end Web team and deals with all aspects of digital strategy. She also serves as executive editor of the group's media Web sites, and you'll even find her byline on, the group's newest site for enterprise developers working with AI. She recently gave a talk at a leading technical publishers conference about how changes in Web technology may impact publishers' bottom lines. Follow her on twitter @beckynagel.

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