Random password generator outputs wrong amount of characters

Question

I started learning C# a few days ago and thought that a random password generator would be a good starter project to do. It worked with letters only but now that I also want to include arrays of numbers and symbols it often outputs the wrong amount of characters like in this example:

Heres my code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;


namespace randompassword
{
    internal class Program
    {
        static void Main(string[] args)
        {
            // Variables
            int pwlength;
            string includeSym;
            string includeNum;

            // Dictionary 
            char[] symbols = { '?', '!', '$', '€', '%' };
            char[] letters = { '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' };
            int[] nums = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };

            Console.Write("Choose your password length: ");
            pwlength = Convert.ToInt32(Console.ReadLine());

            Console.Write("Include numbers (Y/N): ");
            includeNum = Console.ReadLine();
            if (includeNum != "Y" && includeNum != "N")
            {
                Console.WriteLine("Invalid answer - Only answer the letter Y for Yes and N for No! ");
                Console.Write("Include numbers (Y/N): ");
                includeNum = Console.ReadLine();
            }

            Console.Write("Include symbols? (Y/N): ");
            includeSym = Console.ReadLine();
            if (includeSym != "Y" && includeSym != "N")
            {
                Console.WriteLine("Invalid answer - Only answer the letter Y for Yes and N for No! ");
                Console.Write("Include symbols? (Y/N): ");
                includeSym = Console.ReadLine();
            }

            Random rnd = new Random();
            
            for (int z = 1; z <= pwlength; z++)
            {
                int rndList = rnd.Next(1, 4);
                if (rndList == 1)
                {
                    int rndChar = rnd.Next(0, 53);
                    Console.Write(letters[rndChar]);
                }
                else if (rndList == 2)
                {
                    int rndNum = rnd.Next(0, 11);
                    Console.Write(nums[rndNum]);
                }
                else if (rndList == 3)
                {
                    int rndSym = rnd.Next(0, 6);
                    Console.Write(symbols[rndSym]);
                }
            }
            Console.ReadKey();
        }
            

        }

    }

Answer 1

I would suggest something like this instead:

var characters = new List<char>(){ 'a', 'b', ...
Console.Write("Include numbers (Y/N): ");
var includeNum = Console.ReadLine();
if(if (includeNum.ToLower() == "y"){
    characters.AddRange( new []{ '?', '!', '$', '€', '%' });
}
// Do the same for numbers

Console.Write("Choose your password length: ");
var pwlength = Convert.ToInt32(Console.ReadLine());
var password = Enumerable.Range(0, pwLength).Select(i => characters[rnd.Next(0, characters.Count)).ToString();
Console.WriteLine(password);

This should reduce the risk of any index out of bound exceptions, as well as giving a more even probability of characters.

Note that this should only be used for learning. Any proper password generator should use a secure random generator, as well ass omitting similar letters, like I/l and O/0.