Overriding (cast)

Question

If I have a base class and two derived classes, and I want to implement the casting between the two derived classes by hand, is there any way to do that? (in C#)

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Answer 1

You must implement a explicit or implicit operator.

class Imp_A : AbsBase
{
   public static explicit operator Imp_B(Imp_A a)
   {
      Imp_B b = new Imp_B();

      // Do things with b

      return b;
   }
}

Now you can do the following.

Imp_A a = new Imp_A();
Imp_B b = (Imp_B) a;

Answer 2

I'd suggest you write Imp_B like this, if possible:

class Imp_B : Imp_A
{
    private int A;
    private int B;
    private int C;
    private int D;
    private int lastE { get { return this.E.Last(); } }
}

If you can't actually derive from ImpB, it's impossible for you to "treat" a ImpA object as an ImpB transparently the way you'd like, because they just aren't the same thing in memory. So, implement an explicit conversion.