Why should constructors on abstract classes be protected, not public?

ReSharper suggests changing the accessibility of a public constructor in an abstract class to protected, but it does not state the rationale behind this.

Can you shed some light?

Answer

Simply because being public makes no sense in an abstract class. An abstract class by definition cannot be instantiated directly. It can only be instantiated by an instance of a derived type. Therefore the only types that should have access to a constructor are its derived types and hence protected makes much more sense than public. It more accurately describes the accessibility.

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