CODEWITHSUNDEEP
c#.netwindowswinformsshutdown
chersun
chersun

Reputation: 402

C# WinForms Tray application - not catching windows shutdown events

I'm writing a program that monitors state. It launches main window (LoginForm) to ask for user credentials, then hides the form. After that LoginForm inits NotifyIcon and all the remaining work is being done with LoginForm hidden. I've implemented all the clean-up work in FormClosing event of LoginForm. During normal exit process everything works perfectly.

The problem is that the program sits in tray all the time and I tend to forget to exit it before shutting down windows - program doesn't save the state on shutdown event.

I've read through many forums and docs, and from what I've read events FormClosing/FormClosed + SessionEnding/SessionEnded must fire anyway. But it looks like they just don't fire. Can't even cancel shutdown in SessionEnding (with stupid e.Cancel=true) - program disappears without reaching the place.

I've made myself a small debugging library to write out debug information into a file with instant flashing of cache. I've added debug messages to all the events. When I try to log off user in Windows (same as shutting down) for a test - I see no events being triggered usually, just the program vanishes. No exceptions I could catch, no events, etc. When exitting program manually or through "taskkill /IM " - I see all the expected debug printout. What's even more interesting - sometimes the program does reach closing events and does proper clean-up job during Windows shutdown.

Wasted a few days on this already. Overriden WndProc as suggested in MS article - program doesn't reach WndProc as well (to ensure it comes first before closing the form). Tried instead of FormClosing event to override OnClosing of LoginForm - no luck. Added UnhandledException handler, Microsoft.Win32.SessionEnding, Microsoft.Win32.SessionEnded, Form.FormClosing, Form.FormClosed event handlers - no luck.

I suspect this is either a problem of hidden forms or that some kind of exception is happening during shutdown only (resources disposed?). How can I find why that's happening? Is there some simple way to simulate Windows shutdown for single application to make debugging in VS possible? I've tried RMTool - for some reason it fails to simulate shutdown and program just ignores it.

Update: Program uses System.Timers.Timer to regularly poll server for any changes.

Upvotes: 2

Views: 894

Answers (2)

NibblyPig
NibblyPig

Reputation: 52952

I've done some research into this, basically, after Windows XP they altered the way that shutdowns were handled.

You cannot block or capture the shutdown event reliably using the form_closing events etc.

You must use a new API to do so. There is a complete example here: http://bartdesmet.net/blogs/bart/archive/2006/10/25/Windows-Vista-2D00-ShutdownBlockReasonCreate-in-C_2300_.aspx

You should be able to call the function to block shutting down (display a message such as 'saving changes...') and then save and exit your application in the background. Once your program quits, it should allow windows to continue shutting down.

Upvotes: 2

Ahmad
Ahmad

Reputation: 1534

I think windows is simply configured to automatically shutdown all applications regardless and hence the application has no chance to catch SessionEnding events and so on : have a look at http://www.addictivetips.com/windows-tips/disable-automatic-termination-of-applications-during-shutdown-in-windows-7/ or check your configuration at Computer Configurations > Administrative Templates > System > Shutdown Options.

Upvotes: 0

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