ZTK ("Zapple Tool Kit") is a .Net graphical toolkit designed for Wayland compositors written in C# and designed to run in .Net core. It uses Cairo for the rendering.
The ultimate aim is to create a fully managed development environment within Unix-derivative operation systems that is a true first-class citizen rather than just wrapping native toolkits and lagging behind their releases.
This is an incredibly early stage and currently is just a bunch of code I've been playing with for the last couple of weeks. It is loosely modelled on WPF.