[Preview-4] winui Listview control not binding to observable collection within UWP app

[nzstevem]

Describe the bug

Not sure if this should be in ReUnion or not???

The WinUI ListView control is not binding correctly to an Observable collection in a Winui in UWP app.

The very simple code below illustrates the point.

Exactly the same code in a Winui in Desktop works fine, as does the same code in a std non winui UWP app.

Steps to reproduce the bug

Create a new Winui in UWP program and replace the following ...

MainPage.xaml

<StackPanel Orientation="Horizontal" HorizontalAlignment="Center" VerticalAlignment="Center">
    <Button x:Name="myButton" Click="myButton_Click">Click Me</Button>
    <ListView x:Name="myListView" ItemsSource="{x:Bind myItems}"></ListView>
</StackPanel>

MainPage.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using Windows.Foundation;
using Windows.Foundation.Collections;
using Microsoft.UI.Xaml;
using Microsoft.UI.Xaml.Controls;
using Microsoft.UI.Xaml.Controls.Primitives;
using Microsoft.UI.Xaml.Data;
using Microsoft.UI.Xaml.Input;
using Microsoft.UI.Xaml.Media;
using Microsoft.UI.Xaml.Navigation;

using System.Collections.ObjectModel;

// To learn more about WinUI, the WinUI project structure,
// and more about our project templates, see: http://aka.ms/winui-project-info.

namespace TestOBSuwp
{
///

/// An empty page that can be used on its own or navigated to within a Frame.
///

public sealed partial class MainPage : Page
{
ObservableCollection myItems = new ObservableCollection();

    public MainPage()
    {
        this.InitializeComponent();
        myItems.Add($"{DateTime.Now.ToLongTimeString()} Initialized");
    }

    private void myButton_Click(object sender, RoutedEventArgs e)
    {
        myItems.Add($"{DateTime.Now.ToLongTimeString()}");
        myButton.Content = $"Clicked ({myItems.Count})";
    }
}

}

Expected behavior

Expect the ListView to bind to the ObservableCollection.

Screenshots

This screen snip shows std UWP, winui in desktop, and winui in UWP versions of the test code above running.

Clicking the button adds an item to the observable collection and displays the collection count in the button text. The bound ListView should display itims as they are added. The stdUWP and winui in desktop verisons (the top two) work fine. The winui in UWP version only shows the item added in the page init routine even though it is clear the items are being added to the collection. Removing the item add in the init routine results in a completely blank ListView - items are still not added from the click event.

Version Info

NuGet package version:

Windows app type:

UWP	Win32

Windows 10 version	Saw the problem?
Insider Build (21313)

Device form factor	Saw the problem?
Desktop

Additional context

[StephenLPeters]

I think this is because UWP is not currently building against .net5 @stevenbrix can you confirm?

[anawishnoff]

@nzstevem, @StephenLPeters is correct - please see a more detailed explanation of this in our release notes, in the "Known Issues" section under "For C# UWP apps" : Preview 4 Release Notes

[bpulliam]

UWP is no longer supported by WinUI 3. If you can repro the issue on current builds without UWP, please reactivate or open a new issue.

Thanks!