private void btnAddNew_Click(object sender, EventArgs e)
        {
            CustomerRepository customerRepository = new CustomerRepository();
            int result = customerRepository.AddNewDataItem(new Customer()
            {
                FirstName       = txtFirstName.Text,
                LastName        = txtLastName.Text,
                EmailAddress    = txt_EmailAddress.Text,
                TelephoneNumber = txt_TelephoneNumber.Text,
                CreateDate      = DateTime.Now
            });

            if (result != 0)
            {
                GetCustomerList();
                txtFirstName.Text        = string.Empty;
                txtLastName.Text         = string.Empty;
                txt_EmailAddress.Text    = string.Empty;
                txt_TelephoneNumber.Text = string.Empty;
            }
        }