轉：忘了

public class CRC
    {
        #region CRC16
        public static byte[] CRC16(byte[] data)
        {
            int len = data.Length;
            if (len > 0)
            {
                ushort crc = 0xFFFF;

                for (int i = 0; i < len; i++)
                {
                    crc 
 
= (ushort)(crc ^ (data[i]));
                    for (int j = 0; j < 8; j++)
                    {
                        crc = (crc & 1) != 0 ? (ushort)((crc >> 1) ^ 0xA001) : (ushort)(crc >> 1);
                    }
                }
                byte hi = (byte)((crc & 0xFF00) >> 8
 
); //高位置
                byte lo = (byte)(crc & 0x00FF); //低位置

                return new byte[] { hi, lo };
            }
            return new byte[] { 0, 0 };
        }
        #endregion

        #region ToCRC16
        public static string ToCRC16(string content)
        {
            return ToCRC16(content, Encoding.UTF8);
        }

        
 
public static string ToCRC16(string content, bool isReverse)
        {
            return ToCRC16(content, Encoding.UTF8, isReverse);
        }

        public static string ToCRC16(string content, Encoding encoding)
        {
            return ByteToString(CRC16(encoding.GetBytes(content)), true);
        }

        public static string ToCRC16(string content, Encoding encoding, bool isReverse)
        {
            return ByteToString(CRC16(encoding.GetBytes(content)), isReverse);
        }

        public static string ToCRC16(byte[] data)
        {
            return ByteToString(CRC16(data), true);
        }

        public static string ToCRC16(byte[] data, bool isReverse)
        {
            return ByteToString(CRC16(data), isReverse);
        }
        #endregion

        #region ToModbusCRC16
        public static string ToModbusCRC16(string s)
        {
            return ToModbusCRC16(s, true);
        }

        public static string ToModbusCRC16(string s, bool isReverse)
        {
            return ByteToString(CRC16(StringToHexByte(s)), isReverse);
        }

        public static string ToModbusCRC16(byte[] data)
        {
            return ToModbusCRC16(data, true);
        }

        public static string ToModbusCRC16(byte[] data, bool isReverse)
        {
            return ByteToString(CRC16(data), isReverse);
        }
        #endregion

        #region ByteToString
        public static string ByteToString(byte[] arr, bool isReverse)
        {
            try
            {
                byte hi = arr[0], lo = arr[1];
                return Convert.ToString(isReverse ? hi + lo * 0x100 : hi * 0x100 + lo, 16).ToUpper().PadLeft(4, '0');
            }
            catch (Exception ex) { throw (ex); }
        }

        public static string ByteToString(byte[] arr)
        {
            try
            {
                return ByteToString(arr, true);
            }
            catch (Exception ex) { throw (ex); }
        }
        #endregion

        #region StringToHexString
        public static string StringToHexString(string str)
        {
            StringBuilder s = new StringBuilder();
            foreach (short c in str.ToCharArray())
            {
                s.Append(c.ToString("X4"));
            }
            return s.ToString();
        }
        #endregion

        #region StringToHexByte
        private static string ConvertChinese(string str)
        {
            StringBuilder s = new StringBuilder();
            foreach (short c in str.ToCharArray())
            {
                if (c <= 0 || c >= 127)
                {
                    s.Append(c.ToString("X4"));
                }
                else
                {
                    s.Append((char)c);
                }
            }
            return s.ToString();
        }

        private static string FilterChinese(string str)
        {
            StringBuilder s = new StringBuilder();
            foreach (short c in str.ToCharArray())
            {
                if (c > 0 && c < 127)
                {
                    s.Append((char)c);
                }
            }
            return s.ToString();
        }

        /// <summary>
        /// 字串轉16進位制字元陣列
        /// </summary>
        /// <param name="hex"></param>
        /// <returns></returns>
        public static byte[] StringToHexByte(string str)
        {
            return StringToHexByte(str, false);
        }

        /// <summary>
        /// 字串轉16進位制字元陣列
        /// </summary>
        /// <param name="str"></param>
        /// <param name="isFilterChinese">是否過濾掉中文字元</param>
        /// <returns></returns>
        public static byte[] StringToHexByte(string str, bool isFilterChinese)
        {
            string hex = isFilterChinese ? FilterChinese(str) : ConvertChinese(str);

            //清除所有空格
            hex = hex.Replace(" ", "");
            //若字元個數為奇數，補一個0
            hex += hex.Length % 2 != 0 ? "0" : "";

            byte[] result = new byte[hex.Length / 2];
            for (int i = 0, c = result.Length; i < c; i++)
            {
                result[i] = Convert.ToByte(hex.Substring(i * 2, 2), 16);
            }
            return result;
        }
        #endregion
    }