/// <summary>
 /// All this method does is push the supplied instance to the MainViewModel's list of flyouts.
 /// </summary>
 /// <param name="flyoutViewModelBase"></param>
 private void RegisterFlyout(FlyoutViewModelBase flyoutViewModelBase)
 {
     if (flyoutViewModelBase == null) 
         throw new ArgumentNullException("flyoutViewModelBase");
     var flyoutContainer = Util.AppMainWindow.DataContext as IFlyoutContainer;
     if(flyoutContainer != null && flyoutContainer.Flyouts!=null)
     {
         flyoutContainer.Flyouts.Add(flyoutViewModelBase);
     }
 }
 /// <summary>
 /// Registers an instance of <see cref="FlyoutViewModelBase"/> that can be used in the application.
 /// </summary>
 /// <param name="flyoutViewModelBase"></param>
 void IMessagingService.RegisterFlyout(FlyoutViewModelBase flyoutViewModelBase)
 {
     RegisterFlyout(flyoutViewModelBase);
 }