Question

I have a Listbox with data-binding to payments of a project. When I add a new payment, the payment will be added to the list. The add-page is also used to edit the payments. The event is called, in debug-mode I can see the changed value of my payment, but the ListBoxItem is not going to be updated. At the end of the add-page an event will be called, which updates the listbox items:

GlobalNotifier.OnPaymentAdded();

The OnPaymentAdded calls a method which only notifies about the property changes:

OnNotifyPropertyChanged("Project");

The code of the listbox:

<ListBox Name="ListPayments" ItemsSource="{Binding Project.Payments}">
    <ListBox.ItemTemplate>
        <DataTemplate>
            <Grid Margin="10,5,10,0">
                <StackPanel>
                    <TextBlock FontSize="30" Text="{Binding Name}" />
                </StackPanel>
            </Grid>
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>

Why are new items added, but existing items not updated? Any idea?

Answer 1

What’s happening is that although the Project-object is updated, the Payments object (presumably a List) is not.

What you could try is the following:

1. Whenever the List-object is being manipulated (edited, items removed / added), fire the PropertyChanged-event for Projects
2. You can also switch the List<Project> to an ObservableCollection<Project>, which surely will fix your problem
3. If switching to ObservableCollection is out of the question for you, implement an override for the OnNavigatedTo() in the view that shows the list, and call the PropertyChanged-events (Project, Payments etc) from there.

Either one of these should fix your problem – it’s all a matter of taste and preferences.