I work for MS and do Visual Studio integration work for XNA Game Studio.

The whole of VS isn't even close to being mostly managed code. While it is true that 2010's GUI is mostly managed code, thanks to WPF, the internals are entirely COM. The project system, debuggers, command system, and many other large components are all C++/COM. Even many of the components which are managed read more like C++ than like C# due to all the QueryInterface and ref counting nonsense.

Developer devision, commonly known as DevDiv, contains the VS team, programming language teams, and many other related teams. DevDiv is by far the company's largest consumer of managed code. I'd bet that there is more managed code in DevDiv's source tree than the rest of the company combined. That doesn't mean they threw out 30+ years of efforts and backwards compatibility all at once.

I was referring to GUI of Visual Studio - but thanks for the clarification. I didn't mean to imply MS replaced 30 years of code in one go. I should've written more carefully.

I remember watching an interview (on Channel9, probably), that mentioned that Visual C++ had code in it dating back to the 80s.

Props to MS for eating its own dog food if they rewrote everything for .NET

I didn't say they rewrote everything for .NET. There is managed C++ which uses the CLR while also support native C++ code. So they could use code written in the 80's with managed C++.

I seriously doubt they rewrote Visual Studio to be completely managed. That would be incredibly stupid for more than one reason.

But you did authoritatively claim that nearly all of Visual Studio is managed. The conservatism of Visual C++ alone makes me doubt that.

I wrote sloppily. I meant the GUI when I referred to Visual Studio, and not all the compilers, linkers, utilities, etc. I apologize.