Question

I cannot get any display from my observable collection in a custom object bound to a ListBox. This works fine when I have a string collection in my view model, but no names display when I try to access the property through a custom object. I am not receiving any errors in the output window.

Here is my code:

Custom Object

public class TestObject
{
    public ObservableCollection<string> List { get; set; }

    public static TestObject GetList()
    {
        string[] list = new string[] { "Bob", "Bill" };

        return new TestObject
        {
            List = new ObservableCollection<string>(list)
        };
    }
}

Xaml

<Window x:Class="TestWPF.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindow" Height="350" Width="525">
<Grid>
    <ListBox Height="100" HorizontalAlignment="Left" Margin="120,61,0,0" Name="listBox1" VerticalAlignment="Top" Width="120" ItemsSource="{Binding Path=TObj.List}" />
</Grid>

Xaml.cs

    public partial class MainWindow : Window
{
    private ModelMainWindow model;

    public MainWindow()
    {
        InitializeComponent();
        model = new ModelMainWindow();
        this.DataContext = model;
        this.Loaded += new RoutedEventHandler(MainWindow_Loaded);
    }

    public void MainWindow_Loaded(object sender, RoutedEventArgs e)
    {
        this.model.Refresh();
    }
}

ViewModel

    public class ModelMainWindow : INotifyPropertyChanged
{
    private TestObject tObj;

    public event PropertyChangedEventHandler PropertyChanged;

    public TestObject TObj
    {
        get
        {
            return this.tObj;
        }

        set
        {
            this.tObj = value;
            this.Notify("Names");
        }
    }

    public void Notify(string name)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(name));
        }
    }

    public void Refresh()
    {
        this.TObj = TestObject.GetList();
    }
}

Answer 1

Can’t bind to private properties. Also the change notification targets the wrong property, change "Names" to "TObj". (Also i would recommend making the List property get-only (backed by a readonly field), or implementing INoptifyPropertyChanged so the changes cannot get lost)