private void billsButton_Click(object sender, RoutedEventArgs e)
{
appDataGrid.Visibility = Visibility.Visible;
addBill.Visibility = Visibility.Visible;
welcomeLabel.Visibility = Visibility.Hidden;
addInfoButton.Visibility = Visibility.Hidden;
billsList = billsService.GetBillsForUser(Settings.Default.Username).ToList();
appDataGrid.ItemsSource = billsList;
}