Why can't I create an abstract constructor on an abstract C# class?

Question

I am creating an abstract class. I want each of my derived classes to be forced to implement a specific signature of constructor. As such, I did what I would have done has I

Answer 1

All subclasses always can specify their own constructor as long as they call a constructor of the superclass - so there is no way of forcing the a class to have a specific constructor (At least, that is the way it works in Java). You could see of using a factory pattern will get you somewhere - you could define a factory method in an interface - but you'll need a separate factory class as your abstract base class does not know the actual class of the object that needs to be created.

However: maybe adding a more concrete example of the issue you are having might prompt other/better responses. Are you looking for some generic instantiation code, or are you concerned specific settings on the abstract base class have to be done?

If you are just concerned about initialization that has to be done by the abstract class, create a method to do so, and document the usage of that method.

Answer 2

hope this will help someone newb as i am i was looking to make a "normal" public class with a ctor that takes argument and then i needed to make it a child class so i needed an empty ctor for it.

i didnt know this before: if you make a protected ctor then the child class sees it but the rest of the program dont see it (i guess my confusion is since in asp.net i see all the protected in the aspx page which inherits from the cs...)