public partial class AdminPage : Form
    {
        public AdminPage()
        {
            InitializeComponent();
        }

        private void btnEdit_Click(object sender, EventArgs e)
        {

            StreamReader reader = File.OpenText("prices.csv");
            while (!reader.EndOfStream)
            {
                string line = reader.ReadLine();
            }
            reader.Close();
        }

        private void btnSave_Click(object sender, EventArgs e)
        {
            File.WriteAllText("prices.csv");

            this.Hide();

        }
    }

        private void btnView_Click(object sender, EventArgs e)
        {
            AdminLogin vr = new AdminLogin();
            vr.ShowDialog();
        }
    }
}

    class Admin
    {
        //decalre properties
        public string Username { get; set; }
        public string Userpassword { get; set; }

        //intialise
        public Admin(string user, string pass)
        {
            this.Username = user;
            this.Userpassword = pass;
        }
        //validate string
        private bool StringValidator(string input)
        {
            string pattern = "[^a-zA-Z]";
            if (Regex.IsMatch(input, pattern))
            {
                return true;
            }
            else
            {
                return false;
            }
        }
        //validate integer
        private bool IntegerValidator(string input)
        {
            string pattern = "[^0-9]";
            if (Regex.IsMatch(input, pattern))
            {
                return true;
            }
            else
            {
                return false;
            }
        }
        //clear user inputs
        private void ClearTexts(string user, string pass)
        {
            user = String.Empty;
            pass = String.Empty;
        }
        //method to check if eligible to be logged in
        internal bool IsLoggedIn(string user, string pass)
        {
            //check user name empty
            if (string.IsNullOrEmpty(user))
            {
                MessageBox.Show("Enter the user name!");
                return false;

            }
            //check user name is valid type
            else if (StringValidator(user) == true)
            {
                MessageBox.Show("Enter only text here");
                ClearTexts(user, pass);
                return false;
            }
            //check user name is correct
            else
            {
                if (Username != user)
                {
                    MessageBox.Show("User name is incorrect!");
                    ClearTexts(user, pass);
                    return false;
                }
                //check password is empty
                else
                {
                    if (string.IsNullOrEmpty(pass))
                    {
                        MessageBox.Show("Enter the passowrd!");
                        return false;
                    }
                    //check password is valid
                    else if (IntegerValidator(pass) == true)
                    {
                        MessageBox.Show("Enter only integer here");
                        return false;
                    }
                    //check password is correct
                    else if (Userpassword != pass)
                    {
                        MessageBox.Show("Password is incorrect");
                        return false;
                    }
                    else
                    {
                        return true;
                    }
                }
            }
        }
    }
  {


        Login login = new Login("admin", "1234");


        private void button1_Click(object sender, EventArgs e)
        {
            //define local variables from the user inputs
            string user = txtUsername.Text;
            string pass = txtPassword.Text;
            //check if eligible to be logged in
            if (login.IsLoggedIn(user, pass))
            {
                MessageBox.Show("You are logged in successfully");
            }
            else
            {
                //show default login error message
                MessageBox.Show("Login Error!");
            }
        }

        private void linkLabel2_LinkClicked(object sender, LinkLabelLinkClickedEventArgs e)
        {
            //enter your code for forget password case
            MessageBox.Show("Under development");
        }

        private void linkLabel1_LinkClicked(object sender, LinkLabelLinkClickedEventArgs e)
        {
            //Enter your code for registration form of your choice
            MessageBox.Show("Under development");
        }
    }
}