using System;

using System.Linq;

public class Program

{

    const int propertyId = 1223;

    public static void Main()

    {

        Console.WriteLine("ShortCode: {0}", ShortCode.ToShortCode(propertyId));

    }

}    

​

public class ShortCode

    {

        /// <summary>

        ///     No 1s, Ls, 0s, or vowels so bad words can't be spelled

        ///     and letters aren't confused in different fonts.

        ///     The base is the length of the constant string. (Base 28 in this case)

        /// </summary>

        private const string CharacterSet = "B3C7DFG6HJ5KM2NP9QRSTV4WX8YZ";

​

        private const int BitsInLong = 64;

        private const short DefaultLength = 4;

        private const int BaseAmount = 21952;

​

​

        public static int ToInteger(string shortCode)

        {

            if (shortCode.Length < DefaultLength) return 0; // Sliently fail

​

            var reversed = shortCode.ToUpper().ToArray();

​

            var sum = 0;

            var multiplier = 1;

            for (var i = reversed.Length - 1; i >= 0; i--)

            {

                var digit = CharacterSet.IndexOf(reversed[i]);

                if (digit == -1) return 0; // Sliently fail

​

                sum += digit * multiplier;

                multiplier *= CharacterSet.Length;

            }

​

            return Math.Max(sum - BaseAmount, 0);

        }

​

        public static string ToShortCode(int integer)

        {

            if (integer <= 0) return ""; // Silently fail

​

            var code = integer + BaseAmount;

​

            var index = BitsInLong - 1;

            long currentNumber = Math.Abs(code);

            var charArray = new char[BitsInLong];

​

            while (currentNumber != 0)

            {

                var remainder = (int) (currentNumber % CharacterSet.Length);

                charArray[index--] = CharacterSet[remainder];

                currentNumber = currentNumber / CharacterSet.Length;

            }

​

            var result = new string(charArray, index + 1, BitsInLong - index - 1);

​

            return result;

        }

    }