Base conversion is an approach commonly used for URL shorteners. Base conversion helps to convert the same number between its different number representation systems.
The conversion table is
private const string BASE62 = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
999 is converted into
999 = 16 * 62^1 + 7 * 62^0 = "g7"
7 are the 16th and 7th elements of the