private void buttonAccept_Click(object sender, EventArgs e)
        {
            if (testForInvalidValues())
            {
                Customer c = new Customer();

                c.Name         = txtName.TextWithoutWatermark;
                c.LastName     = txtLastName.TextWithoutWatermark;
                c.EmailAddress = txtEmail.TextWithoutWatermark;
                c.PhoneNumber  = txtPhoneNumber.TextWithoutWatermark;
                c.PasswordHash = customerOld.PasswordHash;
                c.Birthday     = DateTime.Parse(txtBirthDate.TextWithoutWatermark);
                c.Street       = txtStreet.TextWithoutWatermark;
                c.HouseNumber  = txtHouseNumber.TextWithoutWatermark;
                c.PLZ          = txtPlz.TextWithoutWatermark;
                c.City         = txtCity.TextWithoutWatermark;
                c.Country      = txtCountry.TextWithoutWatermark;
                c.IsAdmin      = checkAdmin.Checked;

                if (DBController.TryUpdateCustomer(c, customerOld.EmailAddress) == 0)
                {
                    FormController.MainView.UpdateCustomersList();
                    Feedback.SuccessCustomersEdit();

                    if (FormController.CurrentCustomer.EmailAddress == customerOld.EmailAddress)
                    {
                        FormController.CurrentCustomer = c;
                    }
                }
                else
                {
                    Feedback.ErrorDatabaseCustomersEdit();
                }

                ParentForm.Close();
            }
        }