Abstract class vs Protected ​Constructor​s.

So, I am not sure why I want to do abstract class when I can just make my regular class.constructor a protected method. A regular class without public constructor is just like an abstract class. And with protected constructor, the sub-class can also say, public myClass2().Base() as constructor right? (syntax maybe wrong, but you get my point).

The only difference is that public constructor in abstract base class will be available to sub-class without additional work? That's it?

Functionally, they're the same (at least as far as I can tell).

Semantically, they're very different.

that's good to know, thanks. I guess, it is just another, in-your-face kind of annotation to tell others that there is no public constructor available by itself.

There's one very important difference. You can declare methods abstract in an abstract class, which forces all subclasses to implement the method. You can't do that with a concrete class. 

that too, thanks for the tip.

Another is that you can do evil things with Reflection to call protected methods, but theres no way to subvert things to construct an abstract class.

@magicalclick: What prevents me from overriding the abstract class?

@AndyC:

that's good to know too. although not sure why anyone want to do that when they can also simply make a sub-class and call the protected methods? Both approaches want sub-classes anyway. Seems like some people does this and certainly have a good reason, but, why?