//ID Number Section - - - - - - - - - - - - - - - -
//Method OrderID
public string OrderID()
{
return(OrderInitiated.ToShortDateString() + ClientID.ToString() + DateDue.ToShortDateString() + ItemsSold.ToString());
}//end Method OrderID
public override string ToString()
{
return $"ID: {ID} Invoice number: {InvoiceNumber} Year: {Year} Company name: {CompanyName} Total amount: {TotalAmount} Date issued: {DateIssued?.ToShortDateString()} Date due: {DateDue?.ToShortDateString()}";
}