I am modifying an existing WPF, MVVM application (using .NET 8) so that it can support screen readers. For ease, and quick testing, I’m using Windows 11 Narrator, but will also be testing with JAWS.

In general this works, however I’m having a problem whereby when a new item is added to a ListBox, or rather added to an ObservableCollection which is bound to the ListBox, the screen reader doesn’t announce the newly added item.

This is a pretty major issue for our visually impaired users, because items dynamically added to the list are extremely important and require attention. From a sighted users perspective they can instantly see a newly added item, where-as the visually impaired user receives no notification from a screen reader.

I’ve managed to get screen reader notification on a small test app by adding the AutomationProperties.LiveSetting to the Listbox in XAML, retrieving the AutomationPeer for the ListBox and raising the AutomationEvents.LiveRegionChanged when an item is added:

// Do some processing which adds a new item, then retrieve the AutomationPeer to raise the event
var peer = UIElementAutomationPeer.FromElement(MyListBox);
if (peer != null)
{
  peer.RaiseAutomationEvent(AutomationEvents.LiveRegionChanged);
}

This works great in my test app (using code behind), and the screen reader notifies the user of the newly added item.

This is easy to achieve in a small test app using code behind. What I’m trying to figure out, and hope someone can point me in the right direction, is how to achieve this using MVVM.

Using MVVM, I have an ObservableCollection in the view model. So, when an item is added to the ObservableCollection, how can I get the AutomationPeer for the ListBox and raise an automation event within my view model?

Maybe I’m trying to go about this the wrong way, I’m fairly new to both WPF and MVVM.

Here’s my example:

XAML

<Window x:Class="WpfAppAccessibilityTest.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfAppAccessibilityTest"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <ListBox AutomationProperties.LiveSetting="Assertive" AutomationProperties.Name="My list of things" ItemsSource="{Binding ListOfStuff}"/>
    </Grid>
</Window>

Code Behind

using System.Collections.ObjectModel;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Windows.Threading;

namespace WpfAppAccessibilityTest
{
    public class MyViewModel
    {
        Dispatcher dispatcher;

        public MyViewModel()
        {
            dispatcher = Dispatcher.CurrentDispatcher;

            // Simulate handling some event that occurs in the future
            Task.Delay(5000).ContinueWith(_ =>
            {
                dispatcher.Invoke(() =>
                    ListOfStuff.Add("Item2")
                    // How do I raise an AutomationPeer event here so screen reader will anounce the newly added item?
                );
            });
        }

        public ObservableCollection<string> ListOfStuff { get; } = new ObservableCollection<string>() { "Item1" };

    }

    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();

            DataContext = new MyViewModel();
        }
    }
}

I’ve checked this question but none of the answers seemed suitable – I am able to get a screen reader announcing, I just can’t figure out how to do it from the view model.