ShortUrl Generator

 public class UrlGenerator
    {

        private static readonly char[] letters = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789".ToCharArray();

        public static string ConvertToUrl(int number)
        {
            try
            {
                string shortenedUrl = string.Empty;

                while (number > 0)
                {
                    var remainder = number % letters.Length;
                    shortenedUrl += letters[remainder];
                    number = number / letters.Length;
                }

                var reverseResult = shortenedUrl.ToCharArray();

                Array.Reverse(reverseResult);

                string result = new string(reverseResult);

                return result;
            }
            catch (Exception)
            { 
                return string.Empty;
            }
        }

        public static double ConvertToNumber(string url)
        {
            try
            {
                var chrs = url.ToCharArray();
                var result = 0d;

                for (int i = 0; i < chrs.Length; i++)
                {
                    var number = Array.IndexOf(letters, chrs[i]);
                    var power = Math.Pow(letters.Length, chrs.Length - 1 - i);

                    result += number * power;
                }
                return result;
            }
            catch (Exception)
            { 
                return 0;
            }
        }
    }