Extend the ObservableRangeCollection object to recognise when an item is changed

ItemsChangeObservableRangeCollection.cs

using System;
using System.Collections;
using System.Collections.Specialized;
using System.ComponentModel;
using MvvmHelpers;

namespace MyApp.Controls
{
	public class ItemsChangeObservableRangeCollection<T> :
		   ObservableRangeCollection<T> where T : INotifyPropertyChanged
	{

		public delegate void ItemChangedEventHandler(object source, EventArgs args);

		/// <summary>
		/// Event fired when an item of the collection is updated
		/// </summary>
		public event ItemChangedEventHandler ItemChanged;

		protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
		{
			if (e.Action == NotifyCollectionChangedAction.Add)
			{
				RegisterPropertyChanged(e.NewItems);
			}
			else if (e.Action == NotifyCollectionChangedAction.Remove)
			{
				UnRegisterPropertyChanged(e.OldItems);
			}
			else if (e.Action == NotifyCollectionChangedAction.Replace)
			{
				UnRegisterPropertyChanged(e.OldItems);
				RegisterPropertyChanged(e.NewItems);
			}

			base.OnCollectionChanged(e);
		}

		protected override void ClearItems()
		{
			UnRegisterPropertyChanged(this);
			base.ClearItems();
		}

		private void RegisterPropertyChanged(IList items)
		{
			foreach (INotifyPropertyChanged item in items)
			{
				if (item != null)
				{
					item.PropertyChanged += new PropertyChangedEventHandler(item_PropertyChanged);
				}
			}
		}

		private void UnRegisterPropertyChanged(IList items)
		{
			foreach (INotifyPropertyChanged item in items)
			{
				if (item != null)
				{
					item.PropertyChanged -= new PropertyChangedEventHandler(item_PropertyChanged);
				}
			}
		}

		private void item_PropertyChanged(object sender, PropertyChangedEventArgs e)
		{
			OnItemChange(sender);
		}

		protected virtual void OnItemChange(object sender)
		{
			ItemChanged?.Invoke(sender, EventArgs.Empty);
		}
	}
}