Question

Why isn’t this binding working?

<Window x:Class="S3PackageInstaller.MainWindow" x:Name="Window1" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:s3u="clr-namespace:S3PackageInstaller"
    Icon="App.ico" Title="Sims 3 Package Installer" Height="480" Width="740">

    <DockPanel LastChildFill="True">
        <DockPanel DockPanel.Dock="Left" Width="200" VerticalAlignment="Stretch" LastChildFill="True"
            Margin="20,20,0,20">

            <!-- this is the binding that isn't working -->
            <ListView Width="200" ItemsSource="{Binding ElementName=Window1, Path=InstalledPackages}">
                <ListView.View>
                    <GridView>
                        <GridViewColumn Header="Installed Packages" DisplayMemberBinding="{Binding Filename}"></GridViewColumn>
                    </GridView>
                </ListView.View>                
            </ListView>

    <!-- snip -->

</Window>

Relevant code behind:

public partial class MainWindow : Window
{
    public ObservableCollection<object> InstalledPackages { get; private set; }

    public MainWindow()
    {
        InitializeComponent();
        InstalledPackages = new ObservableCollection<object>();
        LoadInstalledPackages();
    }

    private void LoadInstalledPackages()
    {
        var installPath = Settings.Default.TargetDirectory;
        var packages = System.IO.Directory.GetFiles(installPath, "*.package");

        InstalledPackages.Clear();
        foreach (string filename in packages)
            InstalledPackages.Add(new { Filename = filename });
    }

    // snip...
}

When I run the program, the ListView is empty. When debugging, I have verified that the collection contains items after LoadInstalledPackages is run.

Answer 1

I think the problem is that while your collection property is an ObservableCollection, so will notify of collection changes, the property itself does not raise a change notification when you first assign to it. When you create your window as follows:

public MainWindow()
{
    InitializeComponent();
    InstalledPackages = new ObservableCollection<object>();
    LoadInstalledPackages();
}

When InitializeComponent is invoked your UI is created and bindings constructed. At this point InstalledPackages is null. In the next line you create your collection, but because InstalledPackages does not raise a PropertyChanged event, your binding is not updated.

Either implement INotifyPropertyChanged, or assign the ObservableCollection to this property before invoking InitializeComponent.