ObservableCollection Example 2

ObservableCollectionExample2.cs

public void ItemsToBeAddedAreRejectedCorrectlyWhileSomeoneElseIsListening()
{
    var observableCollection = new ObservableCollection<int>();
    observableCollection.CollectionChanged += (o, e) =>
    {
        if (e.Action == NotifyCollectionChangedAction.Add)
        {
            observableCollection.Clear();
        }
    };

    observableCollection.CollectionChanged += (o, e) =>
    {
        // Do nothing on purpose.
    };
    
    observableCollection.Add(13);
    observableCollection.Count.Should().Be(0);
}