using System;

using System.Collections.Generic;

using System.Text;

using System.Linq;

​

Random rnd = new();

const string alphanum = "6NJWcw4OuPQ1oUhv5dIq9KmbkBVytHM0eCzAX7FrS832pLjZEnlasDRfGxTgYi";

GetRandomStrings(30).Take(20).Dump();

​

IEnumerable<string> GetRandomStrings(int maxLen = 100)

{

    while (true)

    {

        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();

    }

}