Thread-safe Silverlight Cairngorm

using System;
using System.Windows;
using System.ComponentModel;
using System.Windows.Threading;

namespace SilverlightCairngorm.Model
{
	/// <summary>
	/// Custom ModelLocator will derive from this abstract class.
	/// 
	/// Custom ModelLocator usually implements Singleton pattern,
	/// please see the example of CairgormEventDispatcher to make the Singleton thread-safe
	/// </summary>
	public abstract class ModelLocator : INotifyPropertyChanged
	{
		//the dispatcher to ensure the PropertyChange event will raised for UI thread to update bound data
		private Dispatcher currentDispatcher;

		protected ModelLocator()
		{
			if (Application.Current != null &&
				Application.Current.RootVisual != null &&  
				Application.Current.RootVisual.Dispatcher != null) 
			{            
				currentDispatcher = Application.Current.RootVisual.Dispatcher;
			}
			else // can't get the Dispatcher, throw an exception 
			{            
				throw new InvalidOperationException("ModelLocator must be initialized after that the RootVisual has been loaded");
			}
		}
		
		#region INotifyPropertyChanged Members

		public event PropertyChangedEventHandler PropertyChanged = delegate { };
		protected void NotifyPropertyChanged(string propertyName)
		{
			//check if we are on the Dispatcher thread if not switch
			if (currentDispatcher.CheckAccess())
				PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
			else
				currentDispatcher.BeginInvoke(new Action<string>(NotifyPropertyChanged), propertyName);
		}

		#endregion

	}
}