Creating an instance of derived class through the base class without hardcoding

Question

My problem is as follows:

I have a base class that needs to be abstract. It has several derived classes, each with their own special properties that are contained in

Answer 1

How are you going to know what type of instance to create? If you'll have an existing instance of the derived class and want to create another instance which is basically identical to it, you should have your base type implement a protected virtual CloneBase method which calls MemberwiseClone and does any deep copying the base type knows about, and a public Clone method which chains to CloneBase and casts to the base type. Each derived types should override CloneBase to chain to base.CloneBase and add any necessary additional deep copying (that step may be omitted if no additional deep-copy logic is required), and also shadow the public Clone method with one that chains to CloneBase and casts the result to its type [using a separate CloneBase makes it possible to both declare a new Clone method with a different signature while also overriding and chaining to the base-class method].

If you'll have an existing instance of the new class, but want its properties to be copied from some other instance, could have an abstract ConstructInstanceLike(x) method which each derived type would implement to either call one of its constructors, or clone itself and modify the clone to match the passed-in object. Neither approach is terribly elegant, but either can work.

If you won't have an existing instance of the new class, you'll need some other means of getting something of the appropriate type. The nicest approach is probably to store a collection of Func delegates, one for each derived type of interest, and then invoke one of those functions to generate an object of one of the associated derived type. It would also be possible to define an interface

IFactory { TResult Create(TParams param); }

but in many cases a delegate will be more convenient to work with.