16

I would like to only implement certain interfaces within other interfaces, I don't want them to be able to be inherited directly by a class.

Thanks in advance!

Improve this question
6
  • 4
    I've re-read the question and I still think you need an example Commented Feb 17, 2010 at 18:42
  • 1
    Reading the question again, I think you're asking for some construct to prevent direct implementation of an interface in a class while not preventing other interfaces to inherit from it. Commented Feb 17, 2010 at 18:44
  • Example: I have an interface called IAnimation, I wish to only implement this interface through an interface INonAnimated or IAnimated. That way both child interfaces hold the same base rules. Commented Feb 17, 2010 at 18:47
  • 1
    Perhaps having the IAnimation interface as an Abstract will allow you to derive two more interfaces from IAnimation as you cannot create an object of it, only derived from it. Commented Feb 17, 2010 at 19:09
  • I wanted to do this to "conditionally require" one property/method or another, but not neither; all of this while maintaining some shared properties/methods in the parent "abstract interface". Commented Feb 7, 2013 at 17:23

3 Answers 3

Reset to default
26

You can't do this in C# - any class can implement any interface it has access to.

Why would you want to do this? Bear in mind that by declaring an interface inheritance:

public interface InterfaceA {}
public interface InterfaceB : InterfaceA {}

You're specifying that anything implementing InterfaceB also has to implement InterfaceA, so you'll get classes implementing InterfaceA anyway.

Improve this answer
Sign up to request clarification or add additional context in comments.

1 Comment

public interface InterfaceA {} public interface InterfaceB : InterfaceA {} public interface InterfaceC : InterfaceA {} InterfaceA would hold the common [i]rules[/i] that I would be using in InterfaceB and InterfaceC
1

First of all, it doesn't make sense to say "implement within other interfaces" because interfaces can't implement anything.

I can see two flawed ways of doing this, sort of.

  1. Make Animated and NonAnimated abstract classes that implement IAnimation. The concrete class below them can still forcibly override your IAnimation methods with the new operator:

    class SomeAnim : Animated
{
    public new void Foo() { }
}

  2. Use mixins. Keep IAnimated and INonAnimated as interfaces, but don't put any methods in your interface. Instead define extension methods like this:

    static class Ext
{
    public static void Foo(this IAnim anim)
    {
        if (anim is IAnimated) // do something
        else if (anim is INonAnimated) // do something else
    }
}

again, a bit of a hack. But what you're trying to do indicates design flaws anyway.

Improve this answer

1 Comment

re code formatting, see here: meta.stackexchange.com/questions/19624/… You need to indent your code by 8 spaces rather than 4
-1

The best I can suggest is to put them -- both the top level and the descended interfaces, in a separate assembly, with the base-level interfaces declared as internal, and the interfaces which extend those interfaces as public.

Improve this answer

2 Comments

Is it then possible to actually implement the top level interfaces, if super-interfaces aren't accessible to the implementing class?
I get this: Inconsistent accessibility: base interface 'IBaseInterface' is less accessible than interface 'IDescendantOfBaseInterface'. C# 4.0.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.