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.
You could use Electron and wire it up with Edge.js resp. electron-edge. Edge.js allows Electron (Node.js) to call .NET DLL files and vice versa.
This way you can write the GUI with HTML, CSS and JavaScript and the backend with .NET Core. Electron itself is also cross platform and based on the Chromium browser.