gistfile1.cs

using System.Collections;
using System.Collections.ObjectModel;
using System.Collections.Specialized;
using System.ComponentModel;
using System.Linq;
using System.Reflection;

namespace XamlPullToRefresh
{
    public class ObservableCollectionEx<T> : ObservableCollection<T>
    {
        private bool? _hasPropertyChanged;
        private bool HasPropertyChanged()
        {
            return _hasPropertyChanged ??
                   (_hasPropertyChanged = typeof(T).GetInterfaces().Contains(typeof(INotifyPropertyChanged))).Value;
        }

        protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
        {
            base.OnCollectionChanged(e);
            if (!(HasPropertyChanged())) return;
            switch (e.Action)
            {
                case NotifyCollectionChangedAction.Add:
                    HandleAdd(e.NewItems);
                    break;
                case NotifyCollectionChangedAction.Remove:
                    HandleRemove(e.OldItems);
                    break;
                case NotifyCollectionChangedAction.Replace:
                case NotifyCollectionChangedAction.Reset:
                    HandleRemove(e.OldItems);
                    HandleAdd(e.NewItems);
                    break;
            }
        }

        private void HandleAdd(IList newItems)
        {
            foreach (var t in newItems.OfType<INotifyPropertyChanged>())
            {
                t.PropertyChanged += ChildrenPropertyChanged;
            }
        }

        private void HandleRemove(IList newItems)
        {
            foreach (var t in newItems.OfType<INotifyPropertyChanged>())
            {
                t.PropertyChanged -= ChildrenPropertyChanged;
            }
        }

        private void ChildrenPropertyChanged(object sender, PropertyChangedEventArgs propertyChangedEventArgs)
        {
            // どこに通知しよっか
        }
    }
}