According to the release note of Xcode 9.3, macOS will remove the support of running 32-bit application without compromise in future version, and they include a 'no32exec' mode in the beta version of macOS 10.13.4 which 32-bit applications will no longer run on.
System.Windows.Forms haven't been port to Cocoa API, so all WinForms apps won't runs on future macOS.
Recently I referenced to XplatUICarbon and managed to make a Cocoa version of XplatUI, but I haven't understand how it works, it would be better if anyone who can give me some thoughts.