IpHelper根據客戶端IP進行網站分流

public class IpHelper
    {
        // 核心方法：IP搜索
       /// <summary>
        /// 查找IP所屬地區，確保web.config存在IPData或者BackIpData配置節
       /// </summary>
       /// <param name="ips">IP</param>
       /// <returns></returns>
        public static IpLocation GetIpLocation(string ips)
        {
            string fn =HttpContext.Current.Server.MapPath(ConfigurationManager.AppSettings["IPData"]);
            string backData = HttpContext.Current.Server.MapPath(ConfigurationManager.AppSettings["BackIpData"]);
            if (!File.Exists(fn))
            {
                if (!File.Exists(backData))
                {
                    throw new Exception("文件不存在");
                }
                fn = backData;
            }
            FileStream fs = new FileStream(fn, FileMode.Open, FileAccess.Read, FileShare.Read);
            BinaryReader fp = new BinaryReader(fs);
            //讀文件頭,獲取首末記錄偏移量
            int fo = fp.ReadInt32();
            int lo = fp.ReadInt32();
            //IP值
            uint ipv = IpStringToInt(ips);
            // 獲取IP索引記錄偏移值
            int rcOffset = getIndexOffset(fs, fp, fo, lo, ipv);
            fs.Seek(rcOffset, System.IO.SeekOrigin.Begin);

            IpLocation ipl;
            if (rcOffset >= 0)
            {
                fs.Seek(rcOffset, System.IO.SeekOrigin.Begin);
                //讀取開頭IP值
                ipl.IpStart = fp.ReadUInt32();
                //轉到記錄體
                fs.Seek(ReadInt24(fp), System.IO.SeekOrigin.Begin);
                //讀取結尾IP值
                ipl.IpEnd = fp.ReadUInt32();
                ipl.Country = GetString(fs, fp);
                ipl.City = GetString(fs, fp);
            }
            else
            {
                //沒找到
                ipl.IpStart = 0;
                ipl.IpEnd = 0;
                ipl.Country = "未知國家";
                ipl.City = "未知地址";
            }
            fp.Close();
            fs.Close();
            return ipl;
        }

        // 函數功能: 采用“二分法”搜索索引區, 定位IP索引記錄位置
        private static int getIndexOffset(FileStream fs, BinaryReader fp, int _fo, int _lo, uint ipv)
        {
            int fo = _fo, lo = _lo;
            int mo;    //中間偏移量
            uint mv;    //中間值
            uint fv, lv; //邊界值
            uint llv;   //邊界末末值
            fs.Seek(fo, System.IO.SeekOrigin.Begin);
            fv = fp.ReadUInt32();
            fs.Seek(lo, System.IO.SeekOrigin.Begin);
            lv = fp.ReadUInt32();
            //臨時作它用,末記錄體偏移量
            mo = ReadInt24(fp);
            fs.Seek(mo, System.IO.SeekOrigin.Begin);
            llv = fp.ReadUInt32();
            //邊界檢測處理
            if (ipv < fv)
                return -1;
            else if (ipv > llv)
                return -1;
            //使用"二分法"確定記錄偏移量
         &nb