private void PayButton_Click(object sender, RoutedEventArgs e)

        {
            if (PayTextBox.Text == "0" || PayTextBox.Text == "")
            {
                MessageBox.Show("Please enter a value greater than 0", "GOLDLINE", MessageBoxButton.OK);
            }
            else if (CustomerIdLabel.Content.ToString() == "" || _selectedCustomer == null)
            {
                MessageBox.Show("Please select a customer", "GOLDLINE", MessageBoxButton.OK);
            }
            else
            {
                CustomerPayment cs = new CustomerPayment(CustomerPayment.GetNextCustomerPaymentId(),
                                                         _selectedCustomer.Id, decimal.Parse(PayTextBox.Text), DateTime.Now, App.CurrentUser.Id);

                MessageBox.Show(CustomerPayment.AddCustomerPayment(cs)
                    ? "Payment was recorded successfully"
                    : "Could not record payment");

                PayTextBox.Text = "";
                ReloadDataGrid();
            }
        }
 public void Test_AddCustomerPayment()
 {
     Assert.IsNull(CustomerPayment.AddCustomerPayment(new CustomerPayment(1, 1, 0, new DateTime(), 1)));
 }