Difference between LocalSettings and IsolatedStorageSettings - windows-phone-8.1

Question

I am building a Windows Phone 8.1 Silverlight App. I am able to use both the following registries:
Windows.Storage.ApplicationData.Current.LocalSettings;
IsolatedStorageSettings.ApplicationSettings;
What are the differeces between these two?
Which one is better?

Answer 1

The difference between Windows.Storage.ApplicationData.Current.LocalSettings and IsolatedStorageSettings.ApplicationSettingsis that the first one is the newer unified Windows Store App API whereas the latter is from the "old" Silverlight API.
New is not always better but I personally think you should go with the modern version here. Both work with Silverlight but if you ever have to migrate your code to WinRT you will save yourself some time since the IsolatedStorageSettings API does not work under WinRT.

Answer 2

There is huge difference in using both settings:
IsolatedStorageSettings works like a Dictionary and it's serialized and saved to IsolatedStorageFile:
IsolatedStorageSettings provide a convenient way to store user specific data as key-value pairs in a local IsolatedStorageFile.
Also note that IsolatedStorageSettings has to be saved - IsolatedStorageSettings.Save. After saving you will find a file __ApplicationSettings in your app's isolated storage.
ApplicationData.LocalSettings is an ApplicationDataContainer. Once you add there a value, it's automatically saved. It's model is conceptually equivalent to the Windows registry.
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.