public class ObservableCollectionBase<T> : ObservableCollection<T>
        where T : INotifyPropertyChanged
    {
        public ObservableCollectionBase()
        {
            this.CollectionChanged += CurrentObservableCollectionChanged;
        }

        void CurrentObservableCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
        {
            if (e.Action == NotifyCollectionChangedAction.Add)
            {
                foreach (T item in e.NewItems)
                {
                    item.PropertyChanged += ItemPropertyChanged;
                }
            } 
            else if (e.Action == NotifyCollectionChangedAction.Remove)
            {
                foreach (T item in e.OldItems)
                {
                    item.PropertyChanged -= ItemPropertyChanged;
                }
            }   
        }

        void ItemPropertyChanged(object sender, PropertyChangedEventArgs e)
        {
            NotifyCollectionChangedEventArgs evarg = new NotifyCollectionChangedEventArgs(
                NotifyCollectionChangedAction.Replace, sender, sender);

            this.OnCollectionChanged(evarg);
        }
    }