Increment an index that uses numbers and characters (aka Base36 numbers)

Question

I have a string based code that can be either two or three characters in length and I am looking for some help in creating a function that will increment it.

Each \'

Answer 1

Maintain the counter as an int and increment this. Convert the int to your character representation by modding and dividing by 36 iterativly. Map the modded range (0-35) to 0-Z.

Example

Updated with functions to go in either direction:

internal class Program
{
    const int Base = 36;

    public static void Main()
    {
        Console.WriteLine(ToInt("0AA"));
        Console.WriteLine(ToString(370));
    }

    private static string ToString(int counter)
    {
        List chars = new List();

        do
        {
            int c = (counter % Base);

            char ascii = (char)(c + (c < 10 ? 48 : 55));

            chars.Add(ascii);
        }
        while ((counter /= Base) != 0);

        chars.Reverse();

        string charCounter = new string(chars.ToArray()).PadLeft(3, '0');

        return charCounter;
    }

    private static int ToInt(string charCounter)
    {
        var chars = charCounter.ToCharArray();

        int counter = 0;

        for (int i = (chars.Length - 1), j = 0; i >= 0; i--, j++)
        {
            int chr = chars[i];

            int value = (chr - (chr > 57 ? 55 : 48)) * (int)Math.Pow(Base, j);

            counter += value;
        }

        return counter;
    }

For more variants of conversion code see Quickest way to convert a base 10 number to any base in .NET?.