protected void registerButton_Click(object sender, EventArgs e)
        {
            if (RegistrationDB.isCustomerExist(userNameTextBox.Text))
            {
                failedLabel.Visible = true;
                return;
            }

            failedLabel.Visible = false;
            string encryptedPwd = LoginUtility.GetEncryptedValue(passwordTextBox.Text);

            RegistrationDB.AddCustomer(firstNameTextBox.Text, lastNameTextBox.Text,
                                       phoneTextBox.Text, cityTextBox.Text,
                                       userNameTextBox.Text, encryptedPwd);
            successLabel.Visible = true;
        }