这不是SSCLI，更不是Mono，而是Microsoft .NET Framework的源代码，源代码和pdb文件将于今年随.NET Framework 3.5和Visual Studio 2008一起发布和公开，开发者将可以利用它们进行调试，开发人员将可以跟踪那些莫名奇妙的异常的来源，Debugging的生活应该会流畅不少吧。但是否能使用这些源代码来构建完整的程序集还是个问题，我认为概率不大。。

We are releasing the source code for .NET Framework base class libraries under the Microsoft Reference License, and the source code will be downloadable and viewable by anyone who accepts the license agreement. 

In addition, Microsoft will introduce a capability in Visual Studio 2008 to allow you to debug into the .NET Framework source code using Visual Studio.  With this capability, when you are stepping through code, you will be able to step into the source code for the .NET base class libraries.

This release will include the Base Class Libraries (BCL), Windows Forms, ASP.NET, System.Data, and WPF. BCL includes many of the basic classes in the framework including collections, string and text handling, IO,serialization, remoting, and others. We plan to include additional libraries into the set as time goes on.

ScottGu has the details.