private static char[] randRonstant =        {        '0','1','2','3','4','5','6','7','8','9','0',        'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z',        'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'        };public static string GenerateRandomNumber(int Length)        {            System.Text.StringBuilder newRandom = new System.Text.StringBuilder(62);            Random rd = new Random();            for (int i = 0; i < Length; i++)            {                newRandom.Append(randRonstant[rd.Next(10)]);            }            return newRandom.ToString();        }public static string GenerateVerificationCode()        {            return GenerateRandomNumber(6);        }