Question

I have an interface with a method Validate() and an abstract class that implement this interface, and made a class called CustomerValidator that inherit the abstract class, also have entity Customer inherit CustomerValidator so i can call customer.Validate() in the library project.

my scenario is that i dont want the validate method to be available on the client code..if they new up a customer they should only see the entity properties..ex fistname ect. How do i hide the validate method? Thanks

Answer 1

I must also ask why Customer inherits CustomerValidator, but also why is CustomerValidator abstract? I would suggest you change your interface and implementation as follows:

public interface ICustomerValidator {
    void Validate(Customer customer);
}

public abstract class CustomerValidator : ICustomerValidator {
    public abstract void Validate(Customer customer);
}

Then, if you insist on being able to do something like

Customer customer = new Customer();
customer.Validate();

I would suggest you use C# extension methods like this:

public static class CustomerExentions {
    public static ICustomerValidator CustomerValidator { get; set; }

    internal static void Validate(this Customer c) {
        if(CustomerValidator == null) {
            throw new InvalidOperationException("CustomerValidator cannot be NULL");
        }

        CustomerValidator.Validate(c);
    }
}

Note the internal scope so that clients cannot use this call.

As for using composition, I don’t think Customer should know anything about CustomerValidator or ICustomerValidator. Those external responsibilities are outside the scope of a Customer class. If anything, CustomerValidator can have a Customer property if you insist on using composition, but I think the interface should take in a Customer parameter instead.