public static ObservableCollection<cls_Invoice> GetData()
        {
            ObservableCollection<cls_Invoice> list = new ObservableCollection<cls_Invoice>();

            cls_Customer customer = new cls_Customer("Bob", 27);
            cls_Product product = new cls_Product(14, "Bike", 85.63);
            DateTime date = new DateTime(2015,12,1);
            cls_Invoice invoice = new cls_Invoice(1,customer, product, date);

            list.Add(invoice);

            customer = new cls_Customer("Tom", 85);
            product = new cls_Product(10, "Snowboard", 105.99);
            date = new DateTime(2015, 11, 30);
            invoice = new cls_Invoice(2, customer, product, date);

            list.Add(invoice);

            customer = new cls_Customer("Jared", 10);
            product = new cls_Product(17, "Kyak", 242.13);
            date = new DateTime(2015, 11, 22);
            invoice = new cls_Invoice(3, customer, product, date);

            list.Add(invoice);

            return list;
        }
 /// <summary>
 /// Constructs an invoice with multiple products
 /// </summary>
 /// <param name="cus">Customer</param>
 /// <param name="prodList">List of Products Purchased</param>
 public cls_Invoice(int id, cls_Customer cust, List<cls_Product> prodList, DateTime d)
 {
     try
     {
         i_invId = id;
         customer = cust;
         productList = prodList;
         date = d;
     }
     catch (Exception ex)
     {
         //Just throw the exception
         throw new Exception(MethodInfo.GetCurrentMethod().DeclaringType.Name + "." +
                             MethodInfo.GetCurrentMethod().Name + " -> " + ex.Message);
     }
 }