Question

I have two classes:

public class Person
{
    public string FirstName
    {
        get { return firstName; }
        set { firstName = value; }
    }
    public string LastName
    {
        get { return lastName; }
        set { lastName = value; }
    }
    public ObservableCollection<AccountDetail> Details
    {
        get { return details; }
        set { details = value; }
    }
    public ObservableCollection<AccountDetail> Phones
    {
        get
        {
            ObservableCollection<AccountDetail> phones;
            phones = new ObservableCollection<AccountDetail>();
            foreach (AccountDetail detail in Details)
            {
                if (detail.Type == DetailType.Phone)
                {
                    phones.Add(detail);
                }
            }
            return phones;
        }
        set
        {
            ObservableCollection<AccountDetail> phones;
            phones = value;
            foreach (AccountDetail detail in Details)
            {
                if (detail.Type == DetailType.Phone)
                {
                    Details.Remove(detail);
                }
            }
            foreach (AccountDetail detail in phones)
            {
                if (!string.IsNullOrEmpty(detail.Value))
                {
                    Details.Add(detail); 
                }
            }
        }
    }

    private string firstName;
    private string lastName;
    private ObservableCollection<AccountDetail> details;
}

and

public class AccountDetail
{
    public DetailType Type
    {
        get { return type; }
        set { type = value; }
    }
    public string Value
    {
        get { return this.value; }
        set { this.value = value; }
    }

    private DetailType type;
    private string value;
}

In my XAML file I have a ListBox named PhonesListBox which is data bound to the phones list (a property of the Person object):

<Window.Resources>

    <!-- Window controller -->
    <contollers:PersonWindowController 
        x:Key="WindowController" />

</Window.Resources>

...

<ListBox 
    Name="PhonesListBox" 
    Margin="0,25,0,0" 
    HorizontalAlignment="Stretch" 
    VerticalAlignment="Top" 
    ItemsSource="{Binding Path=SelectedPerson.Phones, 
                  Source={StaticResource ResourceKey=WindowController}}"
    HorizontalContentAlignment="Stretch" />

...

In its code behind class, there’s a handler for a button which adds a new item to that PhonesListBox:

private void AddPhoneButton_Click(object sender, RoutedEventArgs e)
{
    ObservableCollection<AccountDetail> phones;

    phones = (ObservableCollection<AccountDetail>)PhonesListBox.ItemsSource;
    phones.Add(new AccountDetail(DetailType.Phone));
}

The problem is, the newly added list box item is not added in the person’s details observable collection, i.e. the Phones property is not updated (set is never called). Why? Where am I making a mistake?

Thanks for all the help.

UPDATE: I changed the AddPhoneButton_Click method to:

private void AddPhoneButton_Click(object sender, RoutedEventArgs e)
{
    PersonWindowController windowController;
    ObservableCollection<AccountDetail> details;

    windowController = (PersonWindowController)this.FindResource("WindowController");
    details = windowController.SelectedPerson.Details;
    details.Add(new AccountDetail(DetailType.Phone));
}

This updates the appropriate collection, which is details not Phones (as phones is just a view or a getter of a subset of detail items). Also, I realized I don’t even need the Phones setter. The problem I am facing now is that my UI is not updated with the changes made to the details collection (and subsequently phones). I don’t know how or where to call for the property changed as neither details nor phones are changing; their collection members are. Help. Please.

Answer 1

it sounds like you have an ObservableCollection<AccountDetail> with more than just phones in it, so it looks like you actually need a CollectionViewSource with a Filter added:

public class Person
{
    public ObservableCollection<AccountDetail> Details { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
}


<Window.Resources>
    <CollectionViewSource x:Key="phonesSource" 
        Source="{StaticResource ResourceKey=WindowController}"
            Path="SelectedPerson.Details"  />
</Window.Resources>
<Grid>
    <ListBox 
        Name="PhonesListBox" 
        Margin="0,25,0,0" 
        HorizontalAlignment="Stretch" 
        VerticalAlignment="Top" 
        ItemsSource="{Binding Source={StaticResource phonesSource}}"
        HorizontalContentAlignment="Stretch" />
</Grid>

public MainWindow()
{
    InitializeComponent();
    CollectionViewSource source = 
        (CollectionViewSource)FindResource("phonesSource");
    source.Filter += (o, e) =>
            {
                if (((AccountDetail) e.Item).Type == DetailType.Phone)
                    e.Accepted = true;
            };
}