根据IP地址获得地理位置

    ///<summary>
    /// 提供从纯真IP数据库搜索IP信息的方法；
    ///</summary>
    public class IPSelect
    {
        FileStream ipFile;
        long ip;
        public string ipfilePath; 
        ///<summary>
        /// 构造函数
        ///</summary>
        ///<param name="ipfilePath">纯真IP数据库路径</param>
        public IPSelect()
        {
            ipfilePath = "纯真IP数据库路径";//TextUtility.GetFullPath( Utility.GetIPDbFilePath );
        }

        ///<summary>
        /// 地理位置,包括国家和地区
        ///</summary>
        public struct IPLocation
        {
            public string country, area;
        }

        ///<summary>
        /// 获取指定IP所在地理位置实体
        ///</summary>
        ///<param name="strIP">要查询的IP地址</param>
        ///<returns></returns>
        public string GetIPLocation( string strIP )
        {
            if (!File.Exists(ipfilePath))
            {
                return "";
            }
            ip = IPToLong( strIP );    //将字符串形式的IP转换位long
            IPLocation loc = new IPLocation();
            try
            {
                ipFile = new FileStream(ipfilePath, FileMode.Open, FileAccess.Read);    //文件流
                long[] ipArray = BlockToArray(ReadIPBlock());    //
                long offset = SearchIP(ipArray, 0, ipArray.Length - 1) * 7 + 4;
                ipFile.Position += offset;    //跳过起始IP
                ipFile.Position = ReadLongX(3) + 4;    //跳过结束IP

                int flag = ipFile.ReadByte();    //读取标志
                if (flag == 1)    //表示国家和地区被转向
                {
                    ipFile.Position = ReadLongX(3);
                    flag = ipFile.ReadByte();    //再读标志
                }
                long countryOffset = ipFile.Position;
                loc.country = ReadString(flag);

                if (flag == 2)
                {
                    ipFile.Position = countryOffset + 3;
                }
                flag = ipFile.ReadByte();
                loc.area = ReadString(flag);

                ipFile.Close();
                ipFile = null;
            }
            catch
            {
                return "";
            }
            return loc.country + loc.area;
        }
        ///<summary>
        /// 将字符串形式的IP转换位long
        ///</summary>
        ///<param name="strIP"></param>
        ///<returns></returns>
        public long IPToLong( string strIP )
        {
            byte[] ip_bytes = new byte[8];
            string[] strArr = strIP.Split( new char[] { '.' } );
            for( int i = 0; i < 4; i++ )
            {
                ip_bytes[i] = byte.Parse( strArr[3 - i] );
            }
            return BitConverter.ToInt64( ip_bytes, 0 );
        }
        ///<summary>
        /// 将索引区字节块中的起始IP转换成Long数组
        ///</summary>
        ///<param name="ipBlock"></param>
        long[] BlockToArray( byte[] ipBlock )
        {
            long[] ipArray = new long[ipBlock.Length / 7];
            int ipIndex = 0;
            byte[] temp = new byte[8];
            for( int i = 0; i < ipBlock.Length; i += 7 )
            {
                Array.Copy( ipBlock, i, temp, 0, 4 );
                ipArray[ipIndex] = BitConverter.ToInt64( temp, 0 );
                ipIndex++;
            }
            return ipArray;
        }
        ///<summary>
        /// 从IP数组中搜索指定IP并返回其索引
        ///</summary>
        ///<param name="ipArray">IP数组</param>
        ///<param name="start">指定搜索的起始位置</param>
        ///<param name="end">指定搜索的结束位置</param>
        ///<returns></returns>
        int SearchIP( long[] ipArray, int start, int end )
        {
            int middle = ( start + end ) / 2;
            if( middle == start )
                return middle;
            else if( ip < ipArray[middle] )
                return SearchIP( ipArray, start, middle );
            else
                return SearchIP( ipArray, middle, end );
        }
        ///<summary>
        /// 读取IP文件中索引区块
        ///</summary>
        ///<returns></returns>
        byte[] ReadIPBlock()
        {
            long startPosition = ReadLongX( 4 );
            long endPosition = ReadLongX( 4 );
            long count = ( endPosition - startPosition ) / 7 + 1;//总记录数
            ipFile.Position = startPosition;
            byte[] ipBlock = new byte[count * 7];
            ipFile.Read( ipBlock, 0, ipBlock.Length );
            ipFile.Position = startPosition;
            return ipBlock;
        }
        ///<summary>
        /// 从IP文件中读取指定字节并转换位long
        ///</summary>
        ///<param name="bytesCount">需要转换的字节数，主意不要超过8字节</param>
        ///<returns></returns>
        long ReadLongX( int bytesCount )
        {
            byte[] _bytes = new byte[8];
            ipFile.Read( _bytes, 0, bytesCount );
            return BitConverter.ToInt64( _bytes, 0 );
        }
        ///<summary>
        /// 从IP文件中读取字符串
        ///</summary>
        ///<param name="flag">转向标志</param>
        ///<returns></returns>
        string ReadString( int flag )
        {
            if( flag == 1 || flag == 2 )//转向标志
                ipFile.Position = ReadLongX( 3 );
            else
                ipFile.Position -= 1;

            List<byte> list = new List<byte>();
            byte b = (byte)ipFile.ReadByte();
            while( b > 0 )
            {
                list.Add( b );
                b = (byte)ipFile.ReadByte();
            }
            return Encoding.Default.GetString( list.ToArray() );
        }
    }

        /// <summary>
        /// 根据IP的地理位置
        /// </summary>
        /// <param name="IP">IP</param>
        /// <returns>地理位置</returns>
        protected string GetAddressWithIP(string IP)
        {
            IPSelect IPSelect = new IPSelect();
            if (string.IsNullOrEmpty(IP))
            {
                IP = "127.0.0.1";
            }
            return IPSelect.GetIPLocation(IP);
        }

纯真IP数据库格式文档在【IP数据库文件】