判断真实ip

        #region 获取真实ip
        /// <summary>
        /// 获取真实ip
        /// </summary>
        /// <returns></returns>
        public static string GetRealIP(HttpRequest request)
        {
            string result = String.Empty;

result = request.ServerVariables["HTTP_X_FORWARDED_FOR"];

//可能有代理   
            if (!string.IsNullOrEmpty(result))
            {
                //没有"." 肯定是非IP格式  
                if (result.IndexOf(".") == -1)
                {
                    result = null;
                }
                else
                {
                    //有","，估计多个代理。取第一个不是内网的IP。  
                    if (result.IndexOf(",") != -1)
                    {
                        result = result.Replace(" ", string.Empty).Replace("\"", string.Empty);

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

if (temparyip != null && temparyip.Length > 0)
                        {
                            for (int i = 0; i < temparyip.Length; i++)
                            {
                                //找到不是内网的地址  
                                if (IsIPAddress(temparyip)
                                    && temparyip.Substring(0, 3) != "10."
                                    && temparyip.Substring(0, 7) != "192.168"
                                    && temparyip.Substring(0, 7) != "172.16.")
                                {
                                    return temparyip;
                                }
                            }
                        }
                    }
                    //代理即是IP格式  
                    else if (IsIPAddress(result))
                    {
                        return result;
                    }
                    //代理中的内容非IP  
                    else
                    {
                        result = null;
                    }
                }
            }

if (string.IsNullOrEmpty(result))
            {
                result = request.ServerVariables["REMOTE_ADDR"];
            }

if (string.IsNullOrEmpty(result))
            {
                result = request.UserHostAddress;
            }

return result;
        }

public static bool IsIPAddress(string str)
        {
            if (string.IsNullOrEmpty(str) || str.Length < 7 || str.Length > 15)
                return false;

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

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

return regex.IsMatch(str);
        }   
        #endregion