public void BUG__0002__BulkUpdateFailsWhenCalledFromMultipleThreads()
        {
            var col = new ObservableCollectionEx<int>();

            var t1 =
                Task.Factory.StartNew(() =>
                {
                    using (col.BeginBulkUpdate())
                    {
                        col.Add(1);
                        Thread.Sleep(10);
                    }
                });

            using (col.BeginBulkUpdate())
            {
                col.Clear();
            }

            // code above would normally fail by now.
        }