接口成员是抽象的吗？

Question

Well I know members in an interface act like they were abstract, but are they abstract actually? I mean that I do not need to use that keyword so I am not sure whether its implicit or they are not abstract technically...Hope it makes sense

Answer 1

They are not abstract - they are a contract defined by the interface. "abstract" has a specific meaning which only applies to classes.

That being said, they act very similarly to an abstract member in a class - any type implementing the interface must either implement the member or be abstract itself.

Answer 2

They are abstract in concept, as a class that implements the interface must either implement every member or declare itself to be abstract .

They are not abstract in a technical sense, as only classes are abstract .

Answer 3

Nope. Abstract methods implicitly are virtual.

Interface implementations do not need to be virtual. ( In fact, it is possible to explicitely implement 'conflicting' interfaces (ie interfaces declaring identical member signatures). This would not be possible with the vtable single dispatch [1], because a single vtable slot cannot be filled twice )

[1] classical implementation method for virtual inheritance

Answer 4

They are implicitly abstract in the sense that they have no behavior defined, only the signature of the member is described.

I don't know offhand what it looks like at the IL (and probably will never need to know, actually).