UI not updating even when CollectionChanged or PropertyChanged events are fired - silverlight

Question

Background, from MSDN:
ObservableCollections CollectionChanged event will only be raised
when properties of ObservableCollection are changed (Addition,
deletion of an element) and not when the properties of existing elements are changed.
Bummer, because I need the UI to update when a specific property of an existing element changes. I tried firing both CollectionChanged events and PropertyChanged Events but neither worked.
My situation:
In my application, I have a listbox bound to an observablecollection where the visibility of the items depends on the "Favorite" property of each item using a BoolToVisibilityConverter. XAML:
<ListBox x:Name="FavoritesListBox"
Margin="0,0,-12,0"
ItemsSource="{Binding FeedItemOCollection}"
SelectionChanged="FavoritesListBox_SelectionChanged">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel Name="FavoritesStackPanel"
Margin="0,0,0,17" Visibility="{Binding Favorite, Converter={StaticResource BooltoVisibilityConverter}}">
<TextBlock Text="{Binding Title}"
TextWrapping="Wrap"
Margin="12,0,0,0"
Style="{StaticResource PhoneTextLargeStyle}" />
<TextBlock Text="{Binding PublishDate,Converter={StaticResource DateTimeToDateConverter}}"
TextWrapping="Wrap"
Margin="12,-6,12,0"
Style="{StaticResource PhoneTextSmallStyle}" />
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
Note: This object is initialized in App.Xaml.cs and so is global for the whole application. This may be the unusual thing that is causing things not to work for me.
Once the initial binding occurs, changes to the value of an element's Favorite property does not cause the item to show up or disappear from the Favorites Listbox as is desired for the reason noted at the beginning of the post. This is expected.
To work around this I've tried firing both CollectionChanged events and PropertyChanged Events when the Favorite property is changed to get the UI to update, but neither worked and I'm confused why not. I have succeed in working around my issue, by adding and removing the element from the ObservableCollection, but clearly this is a hack. Code:
public void MarkFavorite(FeedItem feedItem)
{
try
{
feedItem.Favorite = true;
//CollectionChanged(this, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset)); <-- why doesn't this work?
//PropertyChanged(this, new PropertyChangedEventArgs("Count")); <-- why doesn't this work?
this.Remove(feedItem); <-- this works, but is a hack
this.Add(feedItem); <-- this works, but is a hack
SaveToIso();
}
catch (Exception exception)
{
//TODO: Log this.
}
}
Why doesn't firing the events work?
Many thanks ahead of time.

Answer 1

Your FeedItem class must implement INotifyPropertyChanged interface, and your Favorite property must look like:
private bool _Favorite;
private bool _Favorite;
public bool Favorite
{
get { return _Favorite; }
set
{
_Favorite = value;
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs("Favorite"));
}
}
Or you can extract a method
private void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
and your property will look like this:
private bool _Favorite;
public bool Favorite
{
get { return _Favorite; }
set
{
_Favorite = value;
OnPropertyChanged("Favorite");
}
}