windows phone 8, applicationsettings not persisted

Question

I have the following strange behaviour in my Windows phone 8, C# App.

I am saving a Setting with:

private void SaveProperty<T>(T property, string propertyName)
    {
        if (IsolatedStorageSettings.ApplicationSettings.Contains(propertyName))
            IsolatedStorageSettings.ApplicationSettings[propertyName] = property;
        else
            IsolatedStorageSettings.ApplicationSettings.Add(propertyName, property);

        IsolatedStorageSettings.ApplicationSettings.Save();
    }

When the app runs, I can read all settings I stored in IsolatedStorageSettings.ApplicationSettings.

But when I re-open my app (open it from the app list), the IsolatedStorageSettings.ApplicationSettings-Dictionary contains Zero (0) Keys and Values.

Am I missing something?

I used the ISETool.exe to take snapshots of the IsolatedStorage of my app (thanks to chepene). I saw this behaviour: when I wrote the Settings (that means after the SaveProperty<T>() function finished), and the app is still running, I have the Settings saved in _ApplicationSettings. This agrees with my Observation that I can read from the IsolatedStorageSettings.ApplicationSettings when the app is running. The _ApplicationSettings-file also exists when the is tombstoned or not running (when I can Access it by Holding the back-button of the phone and when the app is closed with the back-button).

But when the app is opened again (via the app list), the _ApplicationSettings-file is gone...

I also see that, when I'm writing a file into the IsolatedStorage with:

SharedStorageAccessManager.CopySharedFileAsync(
    Windows.Storage.ApplicationData.Current.LocalFolder, fileName+"orig", 
    Windows.Storage.NameCollisionOption.ReplaceExisting, fileID);

and when I then don't read this file, it is gone when I open the app the next time.

By the way, to avoid confusion: I am not reinstalling the app each time I open it.

If you need more Information please ask.

Any help appreciated.

Answer 1

With AppSettings, I've seen something similar on WP7/7.5, but it happened only when my property-value's type was a class that was not known to the serializer.

Are you sure that there were no exceptions:

• during Save
• during App Exit (since the App may dump the settings at that point)
• during the time that App loads the settings for the first time after launch?

Note that this doesn't necessarily must mean the app crashing. I mean, any exceptions, those internally silenced or user-handled too. Please check the VisualStudio's Output panel for "first chance exceptions" log. If any I/O or security or serialization exception shows up, then investigate there. If i remember well, there's even a whole set of isolated-storage exceptions that are easily interceptable from debug/exceptions menu.

However, the issues I had with unknown or nonserializable types does not explain at all why your extra non-appsettings files would evaporate.

Another thought: maybe some additional tool performs something like 'clean deploy' for you? I don't remember exactly, but I think that VisualStudio's deployment cycle was quite plain:

• rebuild
• remove/uninstall old app from device -- so probably purges isolatedstorage
• install new app onto device

So, maybe that's the cause? Hm.. on afterthought and re-reading your question again, you've said about running the app from the applist, so that rather is not the case. Be sure to check firstchance exceptions then!