Navigation with MVVM on WP7

Example2.cs

using System.Windows.Navigation;
using Microsoft.Practices.Prism.ViewModel;

namespace RememberIt.WP7.App.ViewModels
{
	public abstract class ViewModelBase : NotificationObject
	{
		protected bool RemoveBackEntry { get; set; }

		public NavigationService NavigationService { get; set; }

		public NavigationContext NavigationContext { get; set; }

		public virtual void OnNavigatedTo( NavigationEventArgs e ) {}

		public virtual void OnNavigatingFrom( NavigatingCancelEventArgs e ) {}

		public virtual void OnNavigatedFrom( NavigationEventArgs e )
		{
			if( RemoveBackEntry )
			{
				RemoveBackEntry = false;
				NavigationService.RemoveBackEntry();
			}
		}
	}
}

PageBase.cs

using Microsoft.Phone.Controls;
using RememberIt.WP7.App.ViewModels;

namespace RememberIt.WP7.App.Views
{
	public class PageBase : PhoneApplicationPage
	{
		protected PageBase()
		{
			Loaded += PageBaseLoaded;
		}

		private void PageBaseLoaded( object sender, System.Windows.RoutedEventArgs e )
		{
			var viewModel = DataContext as ViewModelBase;
			if( viewModel != null )
			{
				viewModel.NavigationService = NavigationService;
			}
		}

		protected override void OnNavigatedTo( System.Windows.Navigation.NavigationEventArgs e )
		{
			base.OnNavigatedTo( e );			
			var viewModel = DataContext as ViewModelBase;
			if( viewModel != null )
			{
				viewModel.NavigationContext = NavigationContext;
				viewModel.OnNavigatedTo( e );
			}
		}

		protected override void OnNavigatingFrom( System.Windows.Navigation.NavigatingCancelEventArgs e )
		{
			base.OnNavigatingFrom( e );
			var viewModel = DataContext as ViewModelBase;
			if( viewModel != null )
			{
				viewModel.NavigationContext = NavigationContext;
				viewModel.OnNavigatingFrom( e );
			}
		}

		protected override void OnNavigatedFrom( System.Windows.Navigation.NavigationEventArgs e )
		{
			base.OnNavigatedFrom( e );
			var viewModel = DataContext as ViewModelBase;
			if( viewModel != null )
			{
				viewModel.NavigationContext = NavigationContext;
				viewModel.OnNavigatedFrom( e );
			}
		}
	}
}