gistfile1.cs

using System;
using System.ComponentModel;
using System.Linq.Expressions;
using System.Reflection;

namespace WovenClient.Extensions
{
	// Based on code from http://www.ingebrigtsen.info/post/2008/12/11/INotifyPropertyChanged-revisited.aspx
	public static class NotifyPropertyChangedExtensions
	{
		public static void Notify (this PropertyChangedEventHandler eventHandler, Expression<Func<object>> expression)
		{
			if (eventHandler == null) {
				return;
			}

			MemberExpression memberExpression = expression.Body as MemberExpression;
			if (memberExpression == null) {
				var unaryExpression = expression.Body as UnaryExpression;
				if (unaryExpression != null) {
					memberExpression = unaryExpression.Operand as MemberExpression;
				}
			}
			if (memberExpression == null) {
				return;
			}

			var constantExpression = memberExpression.Expression as ConstantExpression;
			var propertyInfo = memberExpression.Member as PropertyInfo;
			if (constantExpression == null || propertyInfo == null) {
				return;
			}

			foreach (var del in eventHandler.GetInvocationList ()) {
				del.DynamicInvoke (new object [] {
					constantExpression.Value,
					new PropertyChangedEventArgs (propertyInfo.Name)
				});
			}
		}

		public delegate void PropertyChangedHandler<T> (T sender);

		public static void SubscribeToChange<T> (
			this T objectThatNotifies, Expression<Func<object>> expression, PropertyChangedHandler<T> handler)
			where T : INotifyPropertyChanged
		{
			objectThatNotifies.PropertyChanged += (s, e) => {
				MemberExpression memberExpression = expression.Body as MemberExpression;
				if (memberExpression == null) {
					var unaryExpression = expression.Body as UnaryExpression;
					if (unaryExpression != null) {
						memberExpression = unaryExpression.Operand as MemberExpression;
					}
				}
				if (memberExpression == null) {
					return;
				}

				var propertyInfo = memberExpression.Member as PropertyInfo;
				if (propertyInfo == null) {
					return;
				}

				if (e.PropertyName.Equals (propertyInfo.Name)) {
					handler (objectThatNotifies);
				}
			};
		}
	}
}

An example for each of these...subscribe to change on data object, notify UI of change:

        photoGroup.SubscribeToChange (
            () => photoGroup.NewItemCount,
            (g) => {
                PropertyChanged.Notify (() => this.NewCount);
            });