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);
                }
            }
        }
		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);
				}
			}
		}