Update data immediately when modify !

Question

Hello everyone, I have problem with my list data. My data isn't updated when modified. I have two page :
 1. BookPage contains a list of song
  - XAML code :
<ListView Grid.Column="1"
Name="ListViewSong"
IsItemClickEnabled="True"
ItemClick="SongDetail_Click"
Margin="10,0,0,10"
ContinuumNavigationTransitionInfo.ExitElementContainer="True">
<ListView.ItemTemplate>
<DataTemplate>
<StackPanel Holding="ListViewItem_Holding" Width="340"
Margin="0,0,0,15">
<FlyoutBase.AttachedFlyout>
<MenuFlyout>
<MenuFlyoutItem Tag="{Binding}" Click="AddToFavorite_Click"
Text="Thêm vào yêu thích..." />
</MenuFlyout>
</FlyoutBase.AttachedFlyout>
<TextBlock TextAlignment="Center"
Text="{Binding ID,Mode=TwoWay}"
FontSize="22"
Foreground="DodgerBlue" />
<TextBlock Foreground="GreenYellow"
TextWrapping="WrapWholeWords"
TextAlignment="Center"
Text="{Binding FullName,Mode=TwoWay}"
FontSize="18" />
<TextBlock
TextAlignment="Left"
FontSize="12"
Text="{Binding Lyric,Mode=TwoWay}"
Visibility="{Binding Lyric,Converter={StaticResource ConvertTextToVisibility}}"
FontStyle="Italic"
TextTrimming="WordEllipsis" />
<TextBlock
Foreground="Silver"
TextAlignment="Right"
FontSize="14"
Text="{Binding Author,Mode=TwoWay}" Margin="0,0,10,0" />
</StackPanel>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
- Class Song code :
public class Song {
public string ID { get; set; }
public string FullName { get; set; }
public string Lyric { get; set; }
public string Author { get; set; }
public string ShortName { get; set; }
public string NoMarkName { get; set; }
- Load data and Bind to ListView:
public static ObservableCollection<Song> ListAllSongs = new ObservableCollection<Song>();
private async void BookPage_Loaded(object sender, RoutedEventArgs e)
// hiện panel progressbar loading
ProgressBarLoading.Visibility = Visibility.Visible;
ProgressBar.IsIndeterminate = true;
await Task.Delay(1000);
App.ListAllSongs = await App.ViewModel.LoadArirang();
// binding data to Pivo Item "Tat ca"
ListViewSong.ItemsSource = App.ListAllSongs;
// binding data to Pivo Item "Yeu Thich"
ListFavoriteSong.ItemsSource = App.FavoriteSong;
// ẩn panel loading
ProgressBarLoading.Visibility = Visibility.Collapsed;
ProgressBar.IsIndeterminate = false;
// cho phep filter
LeftPanelFilter.IsItemClickEnabled = true;
-- Click any song on the List and navigate to SongDetail Page for modifying. After modify , then save and go back to
BookPage  but data not change on the UI.
protected override void OnNavigatedTo(NavigationEventArgs e)
_song = e.Parameter as Song;
this.DataContext = _song;
private void ButtonBase_OnClick(object sender, RoutedEventArgs e)
var updateSOng = App.ListAllSongs.SingleOrDefault(s => s.ID.Equals(_song.ID));
updateSOng.FullName = txtNewNameTextBlock.Text;
Frame.GoBack();
How could I do that ?
OmegaVN - Window Phone Application Researching and Development

Answer 1

the song class should implement the INotifyPropertyChanged interface so the UI knows the data has been changed and to update itself.
http://msdn.microsoft.com/en-us/library/system.componentmodel.inotifypropertychanged%28v=vs.110%29.aspx
 I use ObservableCollection - it implement interface INotifyPropertyChanged internal ... .I read this  from the Windows Phone 8.1 Development for Absolute Beginners on Channel9.
"Having said all of that, the Hub App Template does not have any classes the directly
implement INotifyPropertyChanged.  Instead, it uses ObservableCollection<T> (as well as a
custom class, ObservableDictionary) which implements the INotifyPropertyChanged interface
internally.  So, the moral to the story is that, as long as we’re using ObservableCollection<T> to
expose collections of the objects from the ViewModel to the View" -
Windows Phone 8.1 Development for Absolute Beginners – Page 199
OmegaVN - Window Phone Application Researching and Development