PasswordValidator

using System;

namespace AP_Question5_BManke
{
    class UserAccount
    {
        private string mUsername;
        private string mPassword;

        public string Username
        {
            get { return mUsername; }
            set
            {
                if (ValidateUsername(value))
                {
                    mUsername = value;
                }
                else
                {
                    throw new Exception("The username must be 3-15 characters long, and contain only alphanumeric characters (letters A-Z, numbers 0-9) and the underscore character(_).");
                }
            }
        }

        public string Password
        {
            get { return mPassword; }
            set
            {
                if (ValidatePassword(value))
                {
                    mPassword = value;
                }
                else
                {
                    throw new Exception("The password must be 8-80 characters long with no spaces, contain at least one upper case and one lower case character, " +
                        "contain a number ranging from 0-9, and have at least one special character (!@#$%^*_=+.?-)");
                }
            }
        }
        public UserAccount()
        {
            mUsername = "user1";
            mPassword = "P@ssword1";
        }
        public UserAccount(string username, string password)
        {
            Username = username;
            Password = password;
        }

        public bool HasSpecialChars(string username)
        {
            return username.Contains("_");
        }

        static bool ValidatePassword(string password)
        {
            const int MIN_LENGTH = 8;
            const int MAX_LENGTH = 80;

            if (password == null) throw new ArgumentNullException();

            bool meetsLengthRequirements = password.Length >= MIN_LENGTH && password.Length <= MAX_LENGTH;
            bool hasUpperCaseLetter = false;
            bool hasLowerCaseLetter = false;
            bool hasDecimalDigit = false;

            if (meetsLengthRequirements)
            {
                foreach (char c in password)
                {
                    if (char.IsUpper(c)) hasUpperCaseLetter = true;
                    else if (char.IsLower(c)) hasLowerCaseLetter = true;
                    else if (char.IsDigit(c)) hasDecimalDigit = true;
                }
            }

            bool isValid = meetsLengthRequirements
                        && hasUpperCaseLetter
                        && hasLowerCaseLetter
                        && hasDecimalDigit
                        ;
            return isValid;

        }
    }