Visual Studio for Windows is mainly written in C# I believe.

moljacsharp · on Nov 14, 2016

Nope.

Most of the UI was rewritten for VS2010 with WPF (XAML, DirectX acceleration), but lower/deeper parts are written in c++ and this makes porting "probelmatic" (MFC, win32.dll, kernel.dll to posix stuff).

MonoDevelop ~ Xamarin.Studio is written in C# (some plugins in F#) and this makes porting easier. That is the reason there was MonoDevelop version on Windows.