GetItemsReport (DateTime? from, DateTime? to) { throw new Not ImplementedException(); } public class Invoice // A unique numerical identifier of an invoice (mandatory) public int Id { get; set; } // A short description of an invoice (optional). public string Description { get; set; } // A number of an invoice e.g. 134/10/2018 (mandatory). public string Number { get; set; } // An issuer of an invoice e.g. Metz-Anderson, 600 Hickman Street, Illinois (mandatory). public string Seller { get; set; } // A buyer of a service or a product e.g. John Smith, 4285 Deercove Drive, Dallas (mandatory). public string Buyer { get; set; I/ A date when an invoice was issued (mandatory). public DateTime CreationDate { get; set; } 1A date when an invoice was paid (optional). public DateTime? AcceptanceDate { get; set; } // A collection of invoice items for a given invoice (can be empty but is never null). public IList InvoiceItems { get; } public Invoice) { InvoiceItems = new List(); } } */ public class InvoiceItem // A name of an item e.g. eggs. public string Name { get; set; } // A number of bought items e.g. 19 public unit Count { get; set; } // A price of an item e.g. 20.5. public decimal Price { get; set; }