/// <summary>
 /// Provides a deterministic way to create the MainViewModel property.
 /// </summary>
 public static void CreateMainViewModel()
 {
     if (_main == null)
     {
         _main = new MainViewModel();
     }
 }
 public void RestoreState()
 {
     using (var store = IsolatedStorageFile.GetUserStoreForApplication())
     {
         if (store.FileExists(STR_MainViewModel))
         {
             using (var stream = store.OpenFile(STR_MainViewModel, FileMode.Open))
             {
                 using (var reader = new StreamReader(stream))
                 {
                     var data = reader.ReadToEnd();
                     var serializer = new XmlSerializer(typeof(MainViewModel));
                     _main = (MainViewModel)serializer.Deserialize(new StringReader(data));
                 }
             }
         }
     }
 }
 /// <summary>
 /// Provides a deterministic way to delete the MainViewModel property.
 /// </summary>
 public static void ClearMainViewModel()
 {
     _main.Cleanup();
     _main = null;
 }