6.18Loops_ConvertHexadecimalNumberToDecimalSystem

using System;

class ConvertHexadecimalNumberToDecimalSystem
{
    static void Main ()
    {
        Console.WriteLine("Enter your Hexadecimal number, without first '0x'-index:");
        Console.Write("HEXADECIMAL NUM = ");
        string hexadecimalStr = Console.ReadLine();
        byte [] hexadecs = new byte [hexadecimalStr.Length];
        for (int i = 0; i < hexadecimalStr.Length; i++)
        {
            hexadecs [i] = ConvertHexadecsToIntegers(hexadecimalStr [i]);
        }
        Array.Reverse(hexadecs);

        long numDecimal = 0;
        long multiplier = 1;
        checked
        {
            foreach (var digit in hexadecs)
            {
                numDecimal += (digit * multiplier);
                multiplier *= 16;
            }
        }

        Console.WriteLine("The Hexadecimal number in Decimal system looks like:");
        Console.WriteLine("DECIMAL NUM = {0} !", numDecimal);
        Console.ReadLine();
    }

    static byte ConvertHexadecsToIntegers (char symbol)
    {
        byte result = 0;
        switch (symbol)
        {
            case '0': result = 0; break;
            case '1': result = 1; break;
            case '2': result = 2; break;
            case '3': result = 3; break;
            case '4': result = 4; break;
            case '5': result = 5; break;
            case '6': result = 6; break;
            case '7': result = 7; break;
            case '8': result = 8; break;
            case '9': result = 9; break;
            case 'A': result = 10; break;
            case 'B': result = 11; break;
            case 'C': result = 12; break;
            case 'D': result = 13; break;
            case 'E': result = 14; break;
            case 'F': result = 15; break;
        }
        return result;
    }
}