private void buttonLogin_Click(object sender, EventArgs e)
        {
            //new Views.AdminForm().Show();
            string username = textBoxUsername.Text;
            string password = textBoxPass.Text;

            var resultA = AdminController.AuthenticateAdmin(username, password);
            var resultE = EmployeeController.AuthenticateEmployee(username, password);
            var resultC = CustomerController.AuthenticateCustomer(username, password);

            if (resultA != null)
            {
                new Views.AdminForm().Show();
            }
            else if (resultE != null)
            {
                new Views.EmployeeForm().Show();
            }
            else if (resultC != null)
            {
                new Views.CustomerForm().Show();
            }

            else
            {
                MessageBox.Show("User not Valid");
            }
        }