private void txtDiscount_TextChanged(object sender, TextChangedEventArgs e)
        {
            if (!string.IsNullOrEmpty(txtDiscount.Text) && int.Parse(txtDiscount.Text.Replace(",", "")) > 0)
            {
                var price = long.Parse(txtDiscount.Text.Replace(",", ""));

                lblDiscount.Content = NumberToString.NumToString(price.ToString()) + " ریال";

                txtDiscount.Text            = price.ToString("N0"); txtDiscount.SelectionStart = txtDiscount.Text.Length;
                txtDiscount.SelectionLength = 0;
            }
            else
            {
                lblDiscount.Content = "";
            }

            CalculateDiscount();
        }
        private void txtRevocationPrice_TextChanged(object sender, TextChangedEventArgs e)
        {
            if (!string.IsNullOrEmpty(txtRevocationPrice.Text))
            {
                var price = long.Parse(txtRevocationPrice.Text.Replace(",", ""));

                txtRevocationPrice.Text = price.ToString("N0");

                lblRevocationPriceText.Content = NumberToString.NumToString(price.ToString()) + " ریال";

                txtRevocationPrice.SelectionStart  = txtRevocationPrice.Text.Length;
                txtRevocationPrice.SelectionLength = 0;
            }
            else
            {
                lblRevocationPriceText.Content = "";
            }
        }