What is the proper way of handling logoff / shutdown / restart when the application has unsaved data?

Question

In WPF App.Current.SessionEnding must return in a few seconds, otherwise the "application does not respond" window appears. So the user can't be asked in this event handler to save his data, because the user's response takes longer than a few seconds.

I thought a solution would be to cancel the logoff / shutdown / restart, and resume it when the user answered to the file save dialog.

    ReasonSessionEnding _reasonSessionEnding;

    App.Current.SessionEnding +=
        new SessionEndingCancelEventHandler(Current_SessionEnding);

    void Current_SessionEnding(object sender, SessionEndingCancelEventArgs e)
    {
        if (_dataModified)
        {
            e.Cancel = true;
            _reasonSessionEnding = e.ReasonSessionEnding;
            Dispatcher.CurrentDispatcher.BeginInvoke(new Action(EndSession));
        }
    }

    void EndSession()
    {
        if (SaveWithConfirmation()) // if the user didn't press Cancel
            //if (_reasonSessionEnding = ReasonSessionEnding.Logoff)
                // logoff
            //else
                // shutdown or restart ?
    }

The problem is that ReasonSessionEnding does not tell me if Windows was shutting down or restarting (it does not differentiate between the two).

So, what should my program do on the session ending event ? Should it even do anything, or doing nothing on this event is the standard ?

The user is asked to save his changes in my main form's OnClosing method, so he does not lose data, but I think that the "application does not respond" window does not suggest a normal workflow.

Canceling the shutdown is not desired I guess, because some of the other programs have been shut down already.

Answer 1

What seems to be the accepted way is to display the save as dialog regardless.

Cancelling the shutdown, then resuming it later is most certainly not an option, for the reason you state and various others.

Since simply discarding the data is unacceptable, there really is no other options.

Well, except to save the data to a temporary file, then automatically restoring them the next time the program is run. Rather like MS Word after it has crashed. Actually, the more I consider it, the better it sounds.

Edit: There's yet another avenue, namely to save continously, the way eg. MS OneNote does. What has struck me before is that, provided you implement decent multilevel undo in your application, the whole manual saving business is actually somewhat dated - an anachronism from the days when disk operations were expensive and error-prone, nowadays mostly old habit.

But I'm digressing. Anyway, it's probably not applicable to your application, since I imagine it needs to be implemented from the beginning.