public class IPHelper

 {

     public static string GetVisitorsIPAddress()

     {

         string result = String.Empty;

         result = System.Web.HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"];

         // 如果使用代理，获取真实IP

         if (result != null && result.IndexOf(".") == -)    //没有“.”肯定是非IPv4格式

             result = null;

         else if (result != null)

         {

             if (result.IndexOf(",") != -)

             {

                 //有“,”，估计多个代理。取第一个不是内网的IP。

                 result = result.Replace(" ", "").Replace("'", "");

                 string[] temparyip = result.Split(",;".ToCharArray());

                 for (int i = ; i < temparyip.Length; i++)

                 {

                     if (IsIPAddress(temparyip[i])

                         && temparyip[i].Substring(, ) != "10."

                         && temparyip[i].Substring(, ) != "192.168"

                         && temparyip[i].Substring(, ) != "172.16.")

                     {

                         return temparyip[i];    //找到不是内网的地址

                     }

                 }

             }

             else if (IsIPAddress(result)) //代理即是IP格式

                 return result;

             else

                 result = null;    //代理中的内容 非IP，取IP

         }

         if (null == result || result == String.Empty)

             result = System.Web.HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];

         if (result == null || result == String.Empty)

             result = System.Web.HttpContext.Current.Request.UserHostAddress;

         return result;

     }

     /// <summary>

     /// 判断是否是IP地址格式 0.0.0.0

     /// </summary>

     /// <param name="str1">待判断的IP地址</param>

     /// <returns>true or false</returns>

     private static bool IsIPAddress(string str1)

     {

         if (str1 == null || str1 == string.Empty || str1.Length <  || str1.Length > ) return false;

         string regformat = @"^\d{1,3}[\.]\d{1,3}[\.]\d{1,3}[\.]\d{1,3}$";

         Regex regex = new Regex(regformat, RegexOptions.IgnoreCase);

         return regex.IsMatch(str1);

     }

 }