Why doesn't application.current.shutdown() work any longer?

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I have a WPF application that, when needed, starts a separate update application and then attempts to close itself down using Application.Current.Shutdown(). This used to work fine. Now it doesn't.

I don't know when this problem started because it's a while since I have had cause to exercise this code (yes, I know, slapped hands for me!).

Does anyone have any idea why this function should now appear to do absolutely nothing at all as far as I can tell?

Any ideas would be welcome.

Kind wishes - Patrick

What I have tried:

I have tried looking at the threads in Process Explorer and the main thread seems to have no other threads running, either foreground or background.

Environment.Exit() does kill the application but apparently is a bit 'rude'.

Posted 17-Mar-21 22:50pm

Patrick Skelton

Updated 18-Mar-21 2:30am

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Patrick Skelton · Answer 1 · 2021-03-18T02:30:00

The solution turns out to be embarrassingly simple. There was no return statement after the call to Application.Current.Shutdown() so the remainder of the Application.OnStartup() method was executing normally.

The details are here: Why does my C# WPF program keep executing lines after Application.Shutdown()? - Stack Overflow[^]

Richard Deeming · Answer 2 · 2021-03-17T22:57:00

Solution 1

Are you trying to call the method from a background thread?

Application.Shutdown Method (System.Windows) | Microsoft Docs[^]:
This method can be called only from the thread that created the Application object.

Posted 17-Mar-21 22:57pm

Richard Deeming

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Patrick Skelton 18-Mar-21 5:14am

Hi, Richard! No, it is being called from Application.Startup(), on the main thread.

Richard Deeming 18-Mar-21 5:20am

Has the Application.Current property been initialized at that point?

If you're in the Startup event, don't you already have a reference to the Application instance?

Richard Deeming 18-Mar-21 5:30am

The other possibility: Do you have a StartupUri defined? As far as I can see, if that's set, it will always be launched after the Startup event fires.

Patrick Skelton 18-Mar-21 5:45am

You are right about using 'this' instead of 'Application'. I've modified the code but there is no change in behaviour. StartupUri is null when I call Shutdown() but does get set later (in code that shouldn't be hit but is unless I do Environment.Exit()). Not sure if it means anything, but a breakpoint just after a call to Shutdown() shows this.Dispatcher.HasShutdownStarted to be false.

Richard Deeming 18-Mar-21 6:59am

The Dispatcher.HasShutdownStarted won't get set until the callback executes, which happens after the Startup event returns, so I'm not surprised it's still false within the event.

I think there must be something else going on in the code. Can you share any of your startup method?

Patrick Skelton 18-Mar-21 7:41am

Mmm... code is not particularly complex but is pretty long. I'll try commenting bits out, to see if I can spot what might be causing the problem.

Patrick Skelton 18-Mar-21 8:30am

Thanks for the help, Richard. Sorry to have wasted your time on what turned out to be a pretty dumb mistake not to have spotted. I've posted the solution I found.