Abstract class implementing interface [modified]

[SeeBees]

There's an abstrat class in .NET public abstract class CollectionBase : IList, ICollection, IEnumerable{...} However, No definition or declaration of IList's functions are found in CollectionBase. How could this ever happen? If it's an abstract class, it's allowed to not implement its interface? Thanks everybody:-D

[PIEBALDconsult]

Yes, only concrete classes must.

[SeeBees]

Thanks, but why won't the following code compile? using System; using System.Collections.Generic; using System.Text; namespace ConsoleApplication1 { interface A{ void A(); } abstract class B : A { // public abstract void A(); } } I got an error! The compiler says I should implement A.A() in abstract class B.

[mav northwind]

That's exactly the same concept - you're not declaring a concrete class anywhere. If you add

class C : B
{
// No implementation of A here as well
}

then you'll get a compiler error.

Regards, mav -- Black holes are the places where God divided by 0...

[SeeBees]

In my previous example, the abstract B results in an error if it doesn't contain method A.A(). So I guess it is necessary to implement an interface even in an abstract class:-O

[PIEBALDconsult]

My earlier answer wasn't quite as correct as I would have preferred. :-D You need the abstract stub, but it's still not an implementation.