Application.Exit() acting odd

Question

Hi All I have written a bit of code to check driver versions and would like to have it installed and run first from an installer. Once the code has executed it should exit as MessageBox.Show(Version of driver is  + Version_Number  MessageBoxButtons.OK MessageBoxIcon.Information); Application.Exit(); It displays a messagebox and should end with Application.Exit() except it does not. it loads the form and waits for a button click at which it displays the message box again and then exits. My question is how to get the program to end after the message box has been shown? (ideally with the form invisible). Glenn

Vulpes · Answer

Application.Exit() is only needed if you're trying to exit the application from a different form (or class) to the main form. If you're on the main form then: this.Close(); should suffice to close the main form and the application as a whole. Also Application.Exit() will cause the FormClosing/FormClosed events to be called for each open form. So if you have any code which handles these events it will be executed before the application closes. If you can't figure out what the problem is then Environment.Exit(1) should kill the application there and then though I'd only use it as a last resort.

Vulpes · Answer

One thing that particularly puzzles me is why you should get an ObjectDisposedException when you call this.Close() and I suspect this is the key to solving the problem. The exception suggests that this is triggering another call to this.Close this.Dispose or Application.Exit. That might happen for instance if you're handling the FormClosing or FormClosed events and have a call to one of those methods in the handler.

Glenn Patton · Answer

Well this is only a small app to check if a driver is installed. I was going to add it to the setup project to give the user a cue to install the driver if it's not installed other wise carry on! Glenn

Vulpes · Answer

Environment.Exit kills the process and all its threads stone dead. However if you have any clean up to do before closing the application such as saving stuff to files then you need to do this first before calling it. One thing that can prevent Application.Exit from working is if you've created your own threads (as opposed to using a BackgroundWorker or the ThreadPool) and have omitted to set the IsBackground property to true for those threads. This property is false by default. The problem here is that an application cannot close normally until all foreground threads have ended so you might have a situation where the UI thread has ended but one or more of your other threads are still running and hence preventing the application from closing. Worse still the UI may have disappeared and so you might not even know that this is happening without checking Task Manager!

Glenn Patton · Answer

Hmm Tried Application.Exit() as said was tried and didn't work Enviroment.Exit(0) seems to do the job nicely. Using this.Close() causes a ObjectDisposedException was unhandled error/warning. If I use Enviroment.Exit(0) I was wondering if it left anything hanging around (such as non-terminated threads) that could come and bite later as it seems to work. Glenn

Vulpes · Answer

The problem with using Environment.Exit is that it doesn't give you any opportunity to clear up before quitting the application. It causes an abrupt exit whereas Application.Exit() causes a more orderly exit.

Glenn Patton · Answer

Thanks for that. I had thanks to google come across Enviroment.Exit(0); and was wondering if there was a penalty for doing this it shall be investigated tomorrow! Thanks Glenn