.NET Framework -> GetClientIp

private string GetClientIp()
{
  string ip = "";

  if (HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"] != null)
  {
      ip = HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"];
      if (!string.IsNullOrEmpty(ip))
      {
          string[] ipRange = ip.Split(",".ToCharArray());
          ip = ipRange[0];
      }
  }

  if (string.IsNullOrEmpty(ip))
  {
      if (HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"] != null)
          ip = HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"].ToString();
  }

  return ip.Trim();
}