C# explicitly implementing an interface with an abstract method

Question

Here is my interface:

public interface MyInterface {
    bool Foo();
}

Here is my abstract class:

public abstract class MyAbstractClass : MyInterface {
    abstract bool MyInterface.Foo();
}

This is the compiler error: "The modifier 'abstract' is not valid for this item.

How should I go on about explicitly implementing an abstract with an abstract method?

Answer 1

I'm not sure why you need to. Why not let the concrete implementation of the abstract class implement the member from the interface? It's the same thing really.

Answer 2

An abstract method has no implementation, so it can't be used to explicitly implement an interface method.

Answer 3

You can't, basically. Not directly, anyway. You can't override a method which is explicitly implementing an interface, and you have to override an abstract method. The closest you could come would be:

bool MyInterface.Foo() {
    return FooImpl();
}

protected abstract bool FooImpl();

That still implements the interface explicitly and forces derived classes to actually provide the implementation. Are those the aspects you're trying to achieve?

Answer 4

You have to use an implicit implementation of the interface member instead of an explicit implementation:

public abstract class MyAbstractClass : MyInterface
{
public abstract bool Foo();
}