string HostName = string.Empty; string ip = string.Empty;string ipv4 = String.Empty;if (!string.IsNullOrEmpty(System.Web.HttpContext.Current.Request.ServerVariables["HTTP_VIA"]))     ip = Convert.ToString(System.Web.HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"]);if (string.IsNullOrEmpty(ip))     ip = Request.UserHostAddress; // 利用 Dns.GetHostEntry 方法，由获取的 IPv6 位址反查 DNS 纪录，
 // 再逐一判断何者为 IPv4 协议，即可转为 IPv4 位址。foreach (IPAddress ipAddr in Dns.GetHostEntry(ip).AddressList){    if (ipAddr.AddressFamily.ToString() == "InterNetwork")    {        ipv4 = ipAddr.ToString();    }}HostName = "主机名: " + Dns.GetHostEntry(ip).HostName + " IP: " + ipv4;