What technology can I use to write one view for my C# application?

What technology can I use to write one view for my C# application?

I'll soon be looking into writing a small business workflow application
that I'd like my userbase to use across all devices - iOS Tablet, Windows
PC, Windows Tablet, Mac, Android Tablet are the key targets.
I'm fairly new to the 'app' dev space and I don't know much about what
frameworks and industry standards are forming around PC and mobile
friendly applications, if any?
I'll be writing the core of the application in C# and I'm looking for
technologies (HTML5, JS, etc) and even frameworks (I saw Xamarin might be
okay?) that implement the View of the application. The tighter its tied to
C# the better it'll be for me and the cleaner the transition between my
chosen platforms the better.