If you want a cross-platform UI from the same codebase, you should use Gtk#, not use Windows.Forms. But that requires a UI rewrite. An alternative is to spli

If you want a cross-platform UI from the same codebase, you should use Gtk#, not use Windows.Forms. But that requires a UI rewrite. An alternative is to split your code along the business logic/presentation layer boundary. Share the business logic and write a platform specific UI using the native toolkit on each platform: WPF or Winforms on Windows, MonoMac (Cocoa) on Mac and Gtk# on Linux. The Winforms stack has not been maintained for about 5 years, and was never particularly debugged nor maintained on Mac. We wanted to remove it, and just tell people "Sorry, this API is useless", but there are a few type dependencies that are needed elsewhere.