获取用户IP地址

        // <summary>
        /// 取得客户端真实IP。如果有代理则取第一个非内网地址
        /// by flower.b
        /// </summary>
        public static string IPAddress
        {
            get
            {
                string result = String.Empty;

                result = HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"];
                if (result != null && result != String.Empty)
                {
                    //可能有代理
                    if (result.IndexOf(".") == -1)    //没有“.”肯定是非IPv4格式
                        result = null;
                    else
                    {
                        if (result.IndexOf(",") != -1)
                        {
                            //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 = 0; i < temparyip.Length; i++)
                            {
                                if (IsIPAddress(temparyip[i])
                                    && temparyip[i].Substring(0, 3) != "10."
                                    && temparyip[i].Substring(0, 7) != "192.168"
                                    && temparyip[i].Substring(0, 7) != "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
                    }

                }

                string IpAddress = (HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"] != null && HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"] != String.Empty) ? HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"] : HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];



                if (null == result || result == String.Empty)
                    result = HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];

                if (result == null || result == String.Empty)
                    result = HttpContext.Current.Request.UserHostAddress;

                return result;
            }
        }