/// <summary>

        /// 将16进制转换为有符号的10进制

        /// </summary>

        /// <param name="hexstr"></param>

        /// <returns></returns>

        public string ConvertHexToSIntStr(string hexstr)

        {

　　　　if (hexstr.StartsWith("0x"))

            {

                hexstr = hexstr.Substring(2);

            }

　　　　//如果不是有效的16进制字符串或者字符串长度大于16或者是空，均返回NULL

　　　if (!IsHexadecimal(hexstr) || hexstr.Length > 16 || string.IsNullOrEmpty(hexstr))

            {

                return null;

            }

            if (hexstr.Length > 8)

            {

                return Convert.ToInt64(hexstr, 16).ToString();

            }

            else  if (hexstr.Length > 4)

            {

                return Convert.ToInt32(hexstr, 16).ToString();

            }

            else

            {

                return Convert.ToInt16(hexstr, 16).ToString();

            }

        }

        /// <summary>

        /// 判断是否是十六进制格式字符串

        /// </summary>

        /// <param name="str"></param>

        /// <returns></returns>

        public bool IsHexadecimal(string str)

        {

            const string PATTERN = @"[A-Fa-f0-9]+$";

            return System.Text.RegularExpressions.Regex.IsMatch(str, PATTERN);

        }