protected void Page_Load(object sender, EventArgs e)
{
    double myNumber = 5123456.00;
    System.Threading.Thread.CurrentThread.CurrentCulture = new CultureInfo("pl-PL");
    Response.Write("<b><u>pl-PL</u></b><br>");
    Response.Write(myNumber.ToString("n") + "<br>");

    System.Threading.Thread.CurrentThread.CurrentCulture = new CultureInfo("en-US");
    Response.Write("<b><u>en-US</u></b><br>");
    Response.Write(myNumber.ToString("n") + "<br>");

    System.Threading.Thread.CurrentThread.CurrentCulture = new CultureInfo("vi-VN");
    Response.Write("<b><u>vi-VN</u></b><br>");
    Response.Write(myNumber.ToString("n") + "<br>");

    System.Threading.Thread.CurrentThread.CurrentCulture = new CultureInfo("fr-CH");
    Response.Write("<b><u>fr-CH</u></b><br>");
    Response.Write(myNumber.ToString("n"));
}
