Check out example codes for "Request.ServerVariables["HTTP_X_FORWARDED_FOR"] get only one ipaddress". It will help you in understanding the concepts better.

Code Example 1

private string GetUserIP()
{
  string ipList = Request.ServerVariables["HTTP_X_FORWARDED_FOR"];

  if (!string.IsNullOrEmpty(ipList))
  {
    return ipList.Split(',')[0];
  }

  return Request.ServerVariables["REMOTE_ADDR"];
}

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