IsolatedStorageSettings.ApplicationSettings are dismissed after App-Restart (WP8)

Question

This happens with the Emulator as well as with the real device, in Debug-Mode as well as in Release-Mode.
In the app I store several application settings successfully - from simple value types to more complex objects and lists of objects.
With "WP POWER TOOLS" I can track the file "__ApplicationSettings" in the root of the IsolatedStorage. It is "well filled" - in the first lines I find some classes and assemblies, that define the complex type definitions, and below the XML starts with the <ArrayOfKeyValueOfstringanyType...> So, everything looks normal to me so far. When I close my app, the last piece of running code is the "Application_Closing"-Handler in App.xaml.cs. In this moment I can check the ApplicationSettings the last time - everything is okay. For example: I check the count of the entries:

var count = System.IO.IsolatedStorage.IsolatedStorageSettings.ApplicationSettings.Count;

...and the count is right and the keys/values are right.

Then - I restart the app at once (Visual-Studio-Debugging is not interrupted) and the first piece of running code is the ctor App() in App.xaml.cs.
In the first line I check the count of ApplicationSettings-Entries again, and: it is 0 !!!
But: WP POWER TOOLS still show me, that the "__ApplicationSettings"-File is existing and is still filled like before. (The consequence of this error is afterwards, that with the first attempt to save any setting again, the whole __ApplicationSettings-File is overwritten and contains just the one new setting.)

So what could be preventing the App from "using" the existing "__ApplicationSettings"-File???

Thanks in advance!

(PS 1: I already experienced, that all ApplicationSettings are destroyed, when there happens an Exception while saving the settings. I investigated all of that already and are 99.9% sure, that there is no Exception anymore.)
(PS 2: Just to make it clear: It is NOT the case, that the complete IsolatedStorage is gone. I have also another file for logging purposes, that I write to the root of the IsolatedStorage. This file is always there. Also the __ApplicationSettings file is not "deleted", it just seems, that the app doesn´t "read" it when launching.)

Answer 1

I tried the repro scenario with an app of mine and confirmed what I expected, that IsolatedStorageSettings.ApplicationSettings.Count was nonzero on entry to the App() ctor upon running the app for a second time in the same emulator process. So there is hope for you to get to this desired state too!

Since you report that the _ApplicationSettings file is not empty, I'll guess 2 possibilities: Maybe an app (or some other process?) keeps the _ApplicationSettings file open when the 2nd run of the app is trying to open the file for reading? MSFT doesn't document how the read is done, so maybe the file is opened with FileShare.None, or with FileShare.Read but some other process still has the file open for writing? I have no idea how to test this on the emulator, but on the real device you might try this scenario:

1. Run the app for the first time, verify it saves a non-empty _ApplicationSettings.
2. Restart the phone device (debugger will disconnect)
3. Run the app for the second time, with a breakpoint in App() ctor.

After 2) I would be confident no other process could have the file open, so the app should be able to read its contents without interference. But if you discover that it still has zero count in 3), then another possibility exists:

Maybe the restarted app encounters an error trying to deserialize the settings from the file into your data structure(s)? The error might not prevent the data from being serialized when the first run of the app is exiting.

To check this possibility, first look for error messages in the Output, Debug window. Do you see any errors when restarting the app the a second time?

If you don't see any helpful error messages, the next thing to try is to simplify the data structures being saved as settings. Try cutting down to just one setting that is a simple type like an int or string. See whether that can be restored correctly, then add more of your settings back into the file until you home in on the one which causes a problem.

Answer 2

Do you call Save on settings? Does it throw any error?