[UWP] NotifyCollectionChangedAction.Add behaves differently while working with custom ObservableCollection

[sethuramkumar]

Describe the bug

Exception throws when using AddRange() for custom observable collection and using OnCollectionChanged as below:

OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add,addedItems));

Same scenario works fine when OnCollectionChanged was used as below:

OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));

Created a custom class based on Observable Collection and declare a method "AddRange()" as below .

public class ObservableRangeCollection<TItem> : ObservableCollection<TItem>
{
    public void AddRange(IEnumerable<TItem> list)
    {
        if (list == null)
            throw new ArgumentNullException(nameof(list));

        IList addedItems = new List<TItem>();
        IList OldList = Items as List<TItem>;
        foreach (TItem item in list)
        {
            Items.Add(item);
            addedItems.Add(item);
        }
        // Exception case
        OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add,addedItems));

        // working case
      //  OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
    }
}

Code used in Model:

public class Model
{
    public string Country { get; set; }

    public Model(string country)
    {
        Country = country;
    }
}

Code Used in ViewModel

public class ViewModel : INotifyPropertyChanged
{

    private ObservableRangeCollection<Model> _countries;

    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }

    public ObservableRangeCollection<Model> Countries
    {
        get { return _countries; }
        set
        {
            _countries = value;
            OnPropertyChanged("Employees");
        }
    }

    public ViewModel() 
    {
        Countries= new ObservableRangeCollection<Model>();
    }
}

Code used in Main Page:

<StackPanel Orientation="Vertical">
    <ListView Width="300" Height="150" Margin="3" ItemsSource="{Binding Countries}" BorderBrush=
        <ListView.ItemTemplate>
            <DataTemplate>
                <TextBlock Text="{Binding Country}"/>
            </DataTemplate>
        </ListView.ItemTemplate>
    </ListView>
    <Button Content="Add Range" Click="Button_Click" Height="30" HorizontalAlignment="Center"/>
</StackPanel>

Code Behind:

private void Button_Click(object sender, RoutedEventArgs e)
{
    List<Model> list = new List<Model>
    {
        new Model("Austria"),new Model("Africa"),new Model("China")
    };
    viewModel.Countries.AddRange(list);
}

Why does OnCollectionChanged with NotifyCollectionChangedAction.Reset as parameter has to be raised for Adding items in the collection?

Note: Sample works fine when OnCollectionChanged() raised with NotifyCollectionChangedAction.Add, addedItems and starting index as parameter.
Exception occurs only when using the OnCollectionChanged with NotifyCollectionChangedAction.Add and addedItems.

Steps to reproduce the bug

1. Declare Custom class based on ObservableCollection.
2. Declare a method to Add range of items and then raise OnCollectionChanged() with NotifyCollecitonChangedAction.Add and addedItems as parameter.

Expected behavior

Exception should not be thrown, items should be properly added in the collection.

Screenshots

Exception Image:

NuGet package version

None

Windows version

Windows 11 (21H2): Build 22000

Additional context

No response

[michael-hawker]

@DmitriyKomin tags were added but no comments/info about what is required here?

Would this maybe be related to what needs to be done to support dotnet/runtime#18087 as well?