I have been developing Windows Forms programs for few years. I am now looking into .NET Core (including ASP.NET Core MVC). I am searching for the new GUI desktop technology.
It is now possible to use Qt, QtQuick, and QML with .NET Core, using Qml.Net.
It is highly performant (not "P/Invoke chatty"), fully featured and works across Linux, OS X, and Windows.
Check out my blog post to see how it compares to the other options out there currently.
PS: I'm the author.