Extension methods for long to convert from/to Base 62. Useful for shrinking long numbers to small strings for URLs (bit.ly like).

gistfile1.cs

 public static string ToBase62(this long input)
 {
     string baseChars = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
     string r = string.Empty;
     int targetBase = baseChars.Length;
     do
     {
         r = string.Format("{0}{1}",
             baseChars[(int)(input % targetBase)],
             r);
         input /= targetBase;
     } while (input > 0);

     return r;
 }

 public static long FromBase62(this string input)
 {
     string baseChars = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
     int srcBase = baseChars.Length;
     long id = 0;
     char[] charArray = input.ToCharArray();
     Array.Reverse(charArray);
     string r = new string(charArray);

     for (int i = 0; i < r.Length; i++)
     {
         int charIndex = baseChars.IndexOf(r[i]);
         id += charIndex * (long)Math.Pow(srcBase, i);
     }

     return id;
 }