private static object CurrentPagePropertyChanged(DependencyObject d, object baseValue)
{
ApplicationPage currentPage = (ApplicationPage)d.GetValue(CurrentPageProperty);
ViewModelBase currentPageViewModel = (ViewModelBase)d.GetValue(CurrentPageViewModelProperty);
var pageHost = (d as PageHost).MainFrame;
pageHost.Content = currentPage.ToBasePage(currentPageViewModel);
return(baseValue);
}