> trying to use .Net in the Windows kernel.

> Microsoft did that, it was called Longhorn

Do you have any reference for that? Or are you confusing Longhorn with Singularity (https://en.wikipedia.org/wiki/Singularity_(operating_system)) / Midori (https://en.wikipedia.org/wiki/Midori_(operating_system))?

I suspect you're referring to the shell/internals, though, not the kernel (https://longhorn.ms/the-reset/#:~:text=Why%20start%20over,re...)

My source for that is I was on the Windows team at Microsoft from 2008-2011. I learned a bunch of this history from talking to coworkers who were there. I specifically recall people talking about c# in the kernel.