//Written by Paul Seal. Licensed under MIT. Free for private and commercial uses.

​

using System;

using System.Text.RegularExpressions;

using CodeShare.Library.Passwords;

public class Program

{

    public static void Main()

    {

        bool includeLowercase = true;

        bool includeUppercase = true;

        bool includeNumeric = true;

        bool includeSpecial = false;

        bool includeSpaces = false;

        int lengthOfPassword  = 16;

        string password = PasswordGenerator.GeneratePassword(includeLowercase, includeUppercase, includeNumeric, includeSpecial, includeSpaces, lengthOfPassword);

        while(!PasswordGenerator.PasswordIsValid(includeLowercase, includeUppercase, includeNumeric, includeSpecial, includeSpaces, password))

        {

            password = PasswordGenerator.GeneratePassword(includeLowercase, includeUppercase, includeNumeric, includeSpecial, includeSpaces, lengthOfPassword);

        }

        Console.WriteLine(password);

    }

}

​

namespace CodeShare.Library.Passwords

{

    public static class PasswordGenerator

    {

        /// <summary>

        /// Generates a random password based on the rules passed in the parameters

        /// </summary>

        /// <param name="includeLowercase">Bool to say if lowercase are required</param>

        /// <param name="includeUppercase">Bool to say if uppercase are required</param>

        /// <param name="includeNumeric">Bool to say if numerics are required</param>

        /// <param name="includeSpecial">Bool to say if special characters are required</param>

        /// <param name="includeSpaces">Bool to say if spaces are required</param>

        /// <param name="lengthOfPassword">Length of password required. Should be between 8 and 128</param>

        /// <returns></returns>

        public static string GeneratePassword(bool includeLowercase, bool includeUppercase, bool includeNumeric, bool includeSpecial, bool includeSpaces, int lengthOfPassword)

        {

            const int MAXIMUM_IDENTICAL_CONSECUTIVE_CHARS = 2;

            const string LOWERCASE_CHARACTERS = "abcdefghijklmnopqrstuvwxyz";

            const string UPPERCASE_CHARACTERS = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

            const string NUMERIC_CHARACTERS = "0123456789";

            const string SPECIAL_CHARACTERS = @"!#$%&*@\";

            const string SPACE_CHARACTER = " ";

            const int PASSWORD_LENGTH_MIN = 8;

            const int PASSWORD_LENGTH_MAX = 128;

​

            if (lengthOfPassword < PASSWORD_LENGTH_MIN || lengthOfPassword > PASSWORD_LENGTH_MAX)

            {

                return "Password length must be between 8 and 128.";

            }

​

            string characterSet = "";

            if (includeLowercase)

            {

                characterSet += LOWERCASE_CHARACTERS;

            }

​

            if (includeUppercase)

            {

                characterSet += UPPERCASE_CHARACTERS;

            }

​

            if (includeNumeric)

            {

                characterSet += NUMERIC_CHARACTERS;

            }

​

            if (includeSpecial)

            {

                characterSet += SPECIAL_CHARACTERS;

            }

​

            if (includeSpaces)

            {

                characterSet += SPACE_CHARACTER;

            }

​

            char[] password = new char[lengthOfPassword];

            int characterSetLength = characterSet.Length;

​

            System.Random random = new System.Random();

            for (int characterPosition = 0; characterPosition < lengthOfPassword; characterPosition++)

            {

                password[characterPosition] = characterSet[random.Next(characterSetLength - 1)];

​

                bool moreThanTwoIdenticalInARow = 

                    characterPosition > MAXIMUM_IDENTICAL_CONSECUTIVE_CHARS

                    && password[characterPosition] == password[characterPosition - 1] 

                    && password[characterPosition - 1] == password[characterPosition - 2];

​

                if (moreThanTwoIdenticalInARow)

                {

                    characterPosition--;

                }

            }

​

            return string.Join(null, password);

        }

        /// <summary>

        /// Checks if the password created is valid

        /// </summary>

        /// <param name="includeLowercase">Bool to say if lowercase are required</param>

        /// <param name="includeUppercase">Bool to say if uppercase are required</param>

        /// <param name="includeNumeric">Bool to say if numerics are required</param>

        /// <param name="includeSpecial">Bool to say if special characters are required</param>

        /// <param name="includeSpaces">Bool to say if spaces are required</param>

        /// <param name="password">Generated password</param>

        /// <returns>True or False to say if the password is valid or not</returns>

        public static bool PasswordIsValid(bool includeLowercase, bool includeUppercase, bool includeNumeric, bool includeSpecial, bool includeSpaces, string password)

        {

            const string REGEX_LOWERCASE = @"[a-z]";

            const string REGEX_UPPERCASE = @"[A-Z]";

            const string REGEX_NUMERIC = @"[\d]";

            const string REGEX_SPECIAL = @"([!#$%&*@\\])+";

            const string REGEX_SPACE = @"([ ])+";

​

            bool lowerCaseIsValid = !includeLowercase || (includeLowercase && Regex.IsMatch(password, REGEX_LOWERCASE));

            bool upperCaseIsValid = !includeUppercase || (includeUppercase && Regex.IsMatch(password, REGEX_UPPERCASE));

            bool numericIsValid = !includeNumeric || (includeNumeric && Regex.IsMatch(password, REGEX_NUMERIC));

            bool symbolsAreValid = !includeSpecial || (includeSpecial && Regex.IsMatch(password, REGEX_SPECIAL));

            bool spacesAreValid = !includeSpaces || (includeSpaces && Regex.IsMatch(password, REGEX_SPACE));

​

            return lowerCaseIsValid && upperCaseIsValid && numericIsValid && symbolsAreValid && spacesAreValid;

        }        

    }

}