Something I encounter, in case you have got system which have thread on the air run in the background and they have their own mechanism of monitoring, in case the application trying to exit Application.Exit, or application.ExitThread, What you think will be, If you think your application is closing, so you are wrong, open the task manager and its still on the air, in previous 1.1 .Net framework it worked properly and application was really exit but now its not, So what you are going to do is To call Environment.Exit(code) and it will close.