ObservableCollection : calling OnCollectionChanged with multiple new items

Question

please note that I am trying to use NotifyCollectionChangedAction.Add action instead of .Reset. the latter does work, but it is not very efficient with large collections.

Answer 1

you can implement AddRange() for the ObservableCollection like this as shown here:

public class RangeObservableCollection : ObservableCollection
{
    private bool _SuppressNotification;

    public override event NotifyCollectionChangedEventHandler CollectionChanged;

    protected virtual void OnCollectionChangedMultiItem(
        NotifyCollectionChangedEventArgs e)
    {
        NotifyCollectionChangedEventHandler handlers = this.CollectionChanged;
        if (handlers != null)
        {
            foreach (NotifyCollectionChangedEventHandler handler in 
                handlers.GetInvocationList())
            {
                if (handler.Target is CollectionView)
                    ((CollectionView)handler.Target).Refresh();
                else
                    handler(this, e);
            }
        }
    }

    protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
    {
        if (!_SuppressNotification)
        {
            base.OnCollectionChanged(e);
            if (CollectionChanged != null)
                CollectionChanged.Invoke(this, e);
        }
    }

    public void AddRange(IEnumerable list)
    {
        if (list == null)
            throw new ArgumentNullException("list");

        _SuppressNotification = true;

        foreach (T item in list)
        {
            Add(item);
        }
        _SuppressNotification = false;

        OnCollectionChangedMultiItem(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, list));
    }
}

UPDATE: After binding to ListBox I was seeing an InvalidOperationException too (same message you were seeing). According to this article that's because CollectionView doesn't support range actions. Luckily the article also supplies a solution (although it feels a little "hack-ish").

UPDATE 2: Added a fix that raises the overridden CollectionChanged event in the overridden implementation of OnCollectionChanged().