private void btnChange_Click(object sender, EventArgs e)
        {
            ChangeForm dialoge = new ChangeForm();

            dialoge.Customer = customerList.SelectedCustomer(this.selectedCustomerCustNr);
            if (DialogResult.Retry == dialoge.ShowDialog())
            {
                customerList.ChangedCustomer(dialoge.Customer);
            }
            UpdateDataGrid();
        }
        public void Customer_ChangeCustomerinList_Pos()
        {
            try
            {
                // arrange

                CustomerList customerList = new CustomerList();
                customerList.ReadCustomerList();
                Customer customer = customerList.Data()[0];
                customer.ChangeLastName = "Biiiinnndder";

                //act
                customerList.ChangedCustomer(customer);
            }
            catch (Exception ex)
            {
                Assert.Fail();
                return;
            }
        }