private void textBoxAddEmail_TextChanged(object sender, EventArgs e)
{
ValidateField(EmailPattern, textBoxAddEmail);
bool invalidExpression = _carService.ExistsCustomer(textBoxAddEmail.Text);
buttonAddNewCustomer.Enabled = !invalidExpression;
labelAddCustomerDisplayInfo.Text = invalidExpression ? "Email is taken." : string.Empty;
}
public bool ExistsCustomer(string email)
{
return(_api.ExistsCustomer(email));
}