PropertyChangedEventHandler null - xaml

Question

I have 2 ObservableCollection<T>s and each of the them has their Cards.
public class Card: INotifyPropertyChanged
{
private string _CardTitle;
public string CardTitle
{
get { return _CardTitle; }
set
{
_CardTitle = value;
OnPropertyChanged("CardTitle");
}
}
public event PropertyChangedEventHandler PropertyChanged;
public void OnPropertyChanged(string name)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(name));
}
}
}
Now when a CardTitle of the card is changed it is reflected on the UI thanks to PropertyChangedEventHandler.
But when I move a card from one collection to another and then change the CardTitle, I get handler as null thus, PropertyChangedEventHandler is not fired and I cannot see the change in UI.
I have scratched my head enough but cannot figure out why. If anyone has any idea then please help me before I get in trouble.

Answer 1

What do you mean by "move"? You remove from first collection, and add to second yes? Does your datacontext implement INotifyPropertyChanged?
I tried to reproduce your code, but i didn't have any problem. Look, maybe you find some hints:
MainPage.xaml.cs
public MainPage()
{
this.InitializeComponent();
this.NavigationCacheMode = NavigationCacheMode.Required;
this.DataContext = this;
}
private ObservableCollection<Card> _first;
public ObservableCollection<Card> First
{
get { return _first; }
set
{
_first = value;
OnPropertyChanged("First");
}
}
private ObservableCollection<Card> _second;
public ObservableCollection<Card> Second
{
get { return _second; }
set
{
_second = value;
OnPropertyChanged("Second");
}
}
protected override void OnNavigatedTo(NavigationEventArgs e)
{
//Init collections
}
private void ChangeItemName(object sender, RoutedEventArgs e)
{
var card = (sender as Button).DataContext as Card;
card.CardTitle = ":)";
}
private void ChangeCollection(object sender, RoutedEventArgs e)
{
var card = (sender as Button).DataContext as Card;
First.Remove(card);
Second.Add(card);
card.CardTitle = "xD";
}
MainPage.xaml
<StackPanel>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition />
<ColumnDefinition />
</Grid.ColumnDefinitions>
<ListView ItemsSource="{Binding First}">
<ListView.ItemTemplate>
<DataTemplate>
<StackPanel>
<TextBlock Text="{Binding CardTitle}" />
<Button Content="Change name" Click="ChangeItemName" />
<Button Content="Change collection" Click="ChangeCollection" />
</StackPanel>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
<ListView ItemsSource="{Binding Second}" Grid.Column="1">
<ListView.ItemTemplate>
<DataTemplate>
<StackPanel>
<TextBlock Text="{Binding CardTitle}" />
<Button Content="Change name" Click="ChangeItemName" />
</StackPanel>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</Grid>
</StackPanel>