private void CurrencyComboBox_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (CurrencyComboBox.SelectedItem != null)
            {
                currentCurrency           = CurrencyComboBox.SelectedItem as CurrencyModel;
                ratesChart.Series[0].Name = currentCurrency.currency_name;

                FlagPictureBox.Image = currentCurrency.Flag();
            }

            FlagPictureBox.Focus();
        }