Should an abstract class have at least one abstract method?

Is it necessary for an abstract class to have at least one abstract method?

The subject of this post and the body ask two different questions:

1. Should it have at least one abstract member?
2. Is it necessary to have at least one abstract member?

The answer to #2 is definitively no.

The answer to #1 is subjective and a matter of style. Personally I would say yes. If your intent is to prevent a class (with no abstract methods) from being instantiated, the best way to handle this is with a privateprotected constructor, not by marking it abstract.