public void SavePersistentData() { var isolatedStorage = IsolatedStorageFile.GetUserStoreForApplication(); var persistentData = new PersistentData { Groups = Groups.Values.ToList(), }; using (var file = isolatedStorage.OpenFile(PERSISTENT_DATA_FILENAME, FileMode.Create, FileAccess.Write)) { using (var writer = new BinaryWriter(file)) { writer.Write(persistentData); } } }