Something that I really miss with the .NET Framework is the source code. In the early days of the Framework between the PDC versions coming out in 2000 and the final release there were a number of rumours about the possibility that the Framework source code might get shipped as an aid to debugging. For a C/C++ developer, this seems natural in that you have the source for the ATL, the MFC and the C runtime library all shipped with Visual Studio and it's a real aid to debugging but the rumours around the .NET Framework source code turned out to be false and the Framework code does not ship with VS. With .NET, it's not so easy. When you wander into the .NET Framework code the best that you've got is the disassembly that's come out of the JIT and most people don't want to step through disassembly these days. At one time, I used to have an idea that all this could be solved by disassembling a .NET Framework assembly back to IL (or maybe even C# via Reflector) and then rebuilding that IL or C# code with debugging information...