Last october Microsoft wrote that they will releae parts of the .Net Framework Sourcecode. This is actually done by now. Microsoft released a Visual Studio 2008 patch that allows to integrate the .Net Sourcecode into the Visual Studio 2008 Debuger. This means that you can step into System-Sourcecode of .Net and that you see the correct call-stack with all the sourcecode contained in there. The cool thing is that the source-code will be downloaded from the Microsoft sourcecode server as needed so you don't need to download all the sourcecode at once. The online-access to the .Net Sourcecode also means that you alwasys will get the sourcecode of the .Net-Version your project is actually running on (.Net 2.0, .Net 3.0, .Net 3.5). Actually not all parts of the .Net-Framework where released now but more will be released in the next weeks and months.

Read more about it here...

How to download and install...