On pressing Alt+F4 an exception is thrown on the _form.Show() line. I’m running MonoGame 3.5 (DX).
internal void RunLoop()
{
// https://bugzilla.novell.com/show_bug.cgi?id=487896
// Since there's existing bug from implementation with mono WinForms since 09'
// Application.Idle is not working as intended
// So we're just going to emulate Application.Run just like Microsoft implementation
Hmmm… I’m not getting it on Windows, DX Monogame 3.6. I doubt it’s the monogame version, but maybe?
Is there a reason this exception is a nuisance for you, though? Since the program is quitting anyway, you could just catch the exception silently and let the program close. It’s not fixing the bug, but it might work temporarily?