There is huge difference in using both settings:
So they are totally different thing, and if you add key to one of above Settings then it won't appear automatically in second. Consider two buttons:
const string firstKey = "firstKey";
const string secondKey = "secondKey";
IsolatedStorageSettings isoSetting = IsolatedStorageSettings.ApplicationSettings;
ApplicationDataContainer localSetting = ApplicationData.Current.LocalSettings;
private void Button_Click(object sender, RoutedEventArgs e)
{
isoSetting.Add(firstKey, true);
localSetting.Values[secondKey] = false;
//isoSetting.Save(); // IsolatedStorageSettings have to be saved
Debug.WriteLine("Is first key in LocalSettings: {0}", localSetting.Values.ContainsKey(firstKey));
Debug.WriteLine("Is first key in ApplicationSettings: {0}", isoSetting.Contains(firstKey));
Debug.WriteLine("Is second key in LocalSettings: {0}", localSetting.Values.ContainsKey(secondKey));
Debug.WriteLine("Is second key in ApplicationSettings: {0}", isoSetting.Contains(secondKey));
}
private void Button_Click2(object sender, RoutedEventArgs e)
{
// run this button after app restart without clicking first button
// and saving IsoSettings
Debug.WriteLine("Is first key in LocalSettings: {0}", localSetting.Values.ContainsKey(firstKey));
Debug.WriteLine("Is first key in ApplicationSettings: {0}", isoSetting.Contains(firstKey));
Debug.WriteLine("Is second key in LocalSettings: {0}", localSetting.Values.ContainsKey(secondKey));
Debug.WriteLine("Is second key in ApplicationSettings: {0}", isoSetting.Contains(secondKey));
}
If I were writing a new app, then I would use new ApplicationData.LocalSettings API - it's newer and it will be much easier to port such an app to RunTime in the future, as WP8.1 RT doesn't support IsolatedStorageSettings.