funny_contracts.cs

public static class InvoiceFactory
{
	public static Invoice CreateByOrder(Order order)
	{
		#region Contract

		Contract.Requires(order != null);
		Contract.Requires(order.PaidDate.HasValue);			
		Contract.Requires(order.Customer != null);

		Contract.Requires(order.NetAmountValue.HasValue);
		Contract.Requires(order.VatAmountValue.HasValue);
		Contract.Requires(order.GrossAmountValue.HasValue);

		Contract.Requires(order.InvoiceContact != null);
		Contract.Requires(order.DeliveryContact != null);			

		#endregion

		// TODO Check order.IsPaid()

		var invoice = new Invoice
		              {
		              	InvoiceDate = order.PaidDate.Value,
		              	InvoiceStatus = InvoiceStatus.Created,
		              	BasedOnOrder = order,
						Customer = order.Customer,
						NetAmountValue = order.NetAmountValue.Value,
						VatAmountValue = order.VatAmountValue.Value,
						GrossAmountValue = order.GrossAmountValue.Value,
						Contact = order.InvoiceContact.Clone(),
						DeliveryContact = order.DeliveryContact.Clone(),
		              };

		foreach (var item in order.Items)
		{
			invoice.DirectAddItem(new InvoiceItem
			                      {
									Invoice = invoice,
			                      	Product = item.OrderProduct,				                      	
									NetAmountValue = item.NetAmountValue,
									VatAmountValue = item.VatAmountValue,
									GrossAmountValue = item.GrossAmountValue,
									Quantity = item.Quantity,
									VatCode = item.VatCode,
									VatPercentage = item.VatPercentage
			                      });
		}


		DomainMessageBus.Publish(new NumberRequestMessage(invoice, SequenceType.Invoice));

		return invoice;
	}
}