Converts integers to ordinal strings.

extensions.cs

    public static class MyExtensions
    {
        public static String ToOrdinalString(this Int32 num)
        {
            switch (num % 100)
            {
                case 11:
                case 12:
                case 13:
                    return num.ToString() + "th";
            }

            switch (num % 10)
            {
                case 1:
                    return num.ToString() + "st";
                case 2:
                    return num.ToString() + "nd";
                case 3:
                    return num.ToString() + "rd";
                default:
                    return num.ToString() + "th";
            }

        }
    }