If you want pure Assembly in binary libraries in C++ and C#, Visual Studio can also display them, one just needs to select the right options.
Indeed it only shows disassembly. I was frustrated that VS wouldn't even show me that. Others write that newer VS lets you enable the showing of assembly.
Anyway, I am spoiled by Java, where I can step into standard library code (which is in Java), can decompile to produce pretty nice Java source where the source is not available, and IntelliJ, which automatically downloads the source where it is publicly available. It's quite wonderful. But I am guessing you already know this, judging from your profile.
To me, not being beholden to documentation is an incredible freedom. The ability to just pop open the source to understand the tool you're working with is indispensable once you've experience that freedom. Microsoft developers don't have this ability, and having had it, it's hard to imagine being without.
ILSpy and Reflector are almost as old as .NET itself.
Visual Studio always had an Assembly view since version 1.0, and there is always WinDbg as alternative, including macro commands to dump .NET JIT information.
Sorry, but it looks like that you haven't properly explored Windows development.
Just the other day I was helping my mom with some C# code in VS, stepping through lines in the debugger. When I hit some library code I excpected to step into the library code, like in Java. Instead it force stepped over. Wouldn’t even let me see a decompile, like XCode shows you for code without available source. That’s microsoft for you. You get some binary libraries, docs that may or may not be crap, and Steve Balmer screaming “developers developers developers” while you bang your head trying to figure out some poorly documented library works. Microsoft relies on users’ ignorance, Stockholm syndrome, and the perception that Apple is more expensive. You get so much more from Apple, it’s incomparable.
That said this acquisition seems like a great fit and doesn’t trouble me at all. As much as I love it, GitHub is nothing special. Microsoft has little to ruin and a lot to improve. Seems like a solid vanity pickup for MSFT, and a good source of guiding vision for GH.