As far as writting C# on the pi. I think you've been able to do this for awhile with Mono .Net
The clr will kill performance as the jvm seems to do already oracle says they have jvm that works well but oracle says lots of things that are at odds with reality.
Maybe MS got a streamlined light version of the CLR with a whole new set of bugs and missing all the features you've come to love?
So much overhead on already stressed hardware when there are much simpler alternatives.
What did the NSA err I mean whoever use for stuxnet virsus? I think the magic combination is lua and c++ I believe that is used for flameas well.
I bring this up because I've seen some amazing things done with very small clean lua programs. Things that you wouldn't mind maintaing a year from now.
Also I don't want my basement flood because my washer has been hacked
I've used perl to great effect on the Pi. Faster than python which is much faster than ruby in my experience.
So many cool things ...
Not insisting using Windows 10 and C# would necessarily be optimal, just easier to work with for me and my 9 year old daughter for now.