private void btnSubmit_Click(object sender, RoutedEventArgs e)
        {
            //https://www.youtube.com/watch?v=RJvKaHPc8Dc
            DB_128040_practiceEntities db = new DB_128040_practiceEntities();


            //string output = $"{Customer.FirstName}/{Customer.LastName}/{Customer.ID}";

            if (int.TryParse(txtBoxInput.Text, out int CustomerID) == true)
            {
                int custID = Convert.ToInt32(txtBoxInput.Text);

                List <Customer> c = new List <Customer>();
                foreach (var x in db.Customers)
                {
                    if (x.CustomerID == custID)
                    {
                        listBoxCustomer.Items.Add(x);
                    }
                }
            }
            else
            {
                string city = txtBoxInput.Text;
                //listBoxCustomer.Items.Add(output);
            }
        }