how to get ip add address whit C# in asp.net

private static string getUserIPAddress()
{
    string sReturn = HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"];
    if (
            (sReturn == null)
            ||
            (sReturn.Length == 0)
            ||
            (sReturn.ToLower().Equals("unknown"))
        )
    {
        sReturn = HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];
    }
    if (sReturn == null) sReturn = string.Empty;
    return sReturn;
}