private void CardNumber_Completed(object sender, System.EventArgs e)
{
if (CardNumber.Text.Length > 16 || CardNumber.Text.Length < 12)
{
ErrorLabel_CardNumber.IsVisible = true;
ErrorLabel_CardNumber.Text = "Invalid card number";
EnableSubmitButton();
}
else
{
ErrorLabel_CardNumber.IsVisible = false;
}
CardNumber.Unfocus();
Month.Focus();
EnableSubmitButton();
}
