static void validate(Invoice invoice)
        {
            InvoiceValidator Validator = new InvoiceValidator();
            Set violations             = Validator.validate(invoice);

            if (violations.size() > 0)
            {
                System.Console.WriteLine("Invoice has (" + violations.size() + ") violations.");
                foreach (ConstraintViolation violation in violations.toArray())
                {
                    System.Console.Write(violation.getMessage() + " @ ");
                    System.Console.Write(violation.getPropertyPath() + "\n");
                }
            }
            else
            {
                System.Console.WriteLine("No Violations in invoice found ");
            }
        }
		static void validate(Invoice invoice){
			
			InvoiceValidator Validator = new InvoiceValidator();
			Set violations = Validator.validate(invoice);  		

			if (violations.size() > 0) {
				System.Console.WriteLine("Invoice has (" + violations.size()  + ") violations.");
				foreach (ConstraintViolation violation in violations.toArray()){
					System.Console.Write (violation.getMessage() + " @ ");
					System.Console.Write (violation.getPropertyPath() + "\n");
				}
			} else {
				System.Console.WriteLine ("No Violations in invoice found ");
			}
		}