using System;
using System.Collections.Generic;
using System.Data;
using System.Text;

namespace ConsoleApp23
{
    class Program
    {
        static void Main(string[] args)
        {
            // 16進制字符串, 0x000000000002654D
            string str = "000000000002654D";// 或者 02654D

            // 16進制字符串 -> bytes
            byte[] a = BytesToHexString(str);

            // bytes -> 16進制字符串
            string hex = BytesToHexString(a);

            // 轉換數值
            long b = Convert.ToInt64(hex, 16);

            Console.Read();
        }

        /// <summary>
        /// 16進制字符串轉byte數組
        /// </summary>
        /// <param name="hexString">16進制字符</param>
        /// <returns></returns>
        public static byte[] BytesToHexString(string hexString)
        {
            // 將16進制秘鑰轉成字節數組
            byte[] bytes = new byte[hexString.Length / 2];
            for (var x = 0; x < bytes.Length; x++)
            {
                var i = Convert.ToInt32(hexString.Substring(x * 2, 2), 16);
                bytes[x] = (byte)i;
            }
            return bytes;
        }

        /// <summary>
        /// byte數組轉16進制字符串
        /// </summary>
        /// <param name="bytes">byte數組</param>
        /// <returns></returns>
        public static string BytesToHexString(byte[] bytes)
        {
            StringBuilder sb = new StringBuilder(bytes.Length * 3);
            foreach (byte b in bytes)
            {
                sb.Append(Convert.ToString(b, 16).PadLeft(2, '0'));
            }
            return sb.ToString().ToUpper();
        }
    }
}