private void m_txt_so_tien_Leave(object sender, EventArgs e)
{
Double value;
if (Double.TryParse(m_txt_so_tien.Text, out value))
{
m_so_tien = value;
m_txt_so_tien.Text = String.Format(System.Globalization.CultureInfo.CurrentCulture, "{0:C2}", value);
}
else
m_txt_so_tien.Text = String.Empty;
}