using System.Collections.Generic;
const string alphanum = "6NJWcw4OuPQ1oUhv5dIq9KmbkBVytHM0eCzAX7FrS832pLjZEnlasDRfGxTgYi";
GetRandomStrings(30).Take(20).Dump();
IEnumerable<string> GetRandomStrings(int maxLen = 100)
StringBuilder sb = new(rnd.Next(maxLen));
for(int i = 0; i < sb.Capacity; i++)
sb.Append(alphanum[rnd.Next(0, alphanum.Length)]);
yield return sb.ToString();