public class CustomersBiz {
public CustomersList ListCustomers(CustomersFilter request) {
// kd vynechn ...
var customers =
from c in northwind.Customers
where ( (String.IsNullOrEmpty(request.Country)
	|| c.Country == request.Country)
&& (String.IsNullOrEmpty(request.Region)
	|| c.Region == request.Region))
select c;

		return (new CustomersList(customers));
}
}
