using System;

using System.Security.Cryptography;

public class Program

{

    public static void Main()

    {

        Console.WriteLine(GenerateRandomString(10));

        Console.WriteLine(GenRandomStrings(10));

    }

    // old logic

    private static string GenerateRandomString(int length)

    {

        var random = new Random();

        var allowedChars = "abcdefghjkmnpqrstuvwxyzABCDEFGHJKMNPQRSTUVWXYZ23456789";

        var newPassword = string.Empty;

        for (int i = 0; i < length; i++)

        {

            newPassword += allowedChars[random.Next(allowedChars.Length)];

        }

​

        return newPassword;

    }

    // replace with new logic below

    private static string GenRandomStrings(int strLen)

    {

        var result = string.Empty;

​

        using (var gen = new RNGCryptoServiceProvider())

        {

            var data = new byte[1];

​

            while (result.Length < strLen)

            {

                gen.GetNonZeroBytes(data);

                int code = data[0];

                if (code > 48 && code < 57 || // 0-9

                    code > 65 && code < 90 || // A-Z

                    code > 97 && code < 122   // a-z

                )

                {

                    result += Convert.ToChar(code);

                }

            }

​

            return result;

        }

    }

}