Looking for Clone() implementation with derived return Type

Question

I am sure this must be a duplicate, but I can't find the answer:

If I have two classes:

public class BASE
{
    public BASE() {};
    public abstract BASE clone();
}


public class CHILD : BASE
{

    public CHILD() : base() {}
    public override BASE clone()
    {
        return new CHILD();
    }
}

I have to make an explicit conversion every time I want to clone an object of type CHILD like:

var a = new CHILD();
CHILD b = a.clone() as CHILD;

Is there a way to avoid this conversion? I would like to be able to write:

var original = new CHILD();
BASE copy1 = original.clone();
CHILD copy2 = original.clone();

Is this possible in C#?

Answer 1

Is there a way to avoid this conversion?

Not by overloading Clone - you can't overload a method just by changing its return type. Use a different method instead:

public class CHILD : BASE
{

    public CHILD() : base() {}
    public BASE clone() { return this.cloneChild();}
    public CHILD cloneChild()
    {
        return new CHILD();
    }
}

If you want to enforce that behavior on all inherited classes you could make BASE generic:

public abstract class BASE<T> where T:BASE<T>
{
    public BASE() {}
    public abstract T clone();
}


public class CHILD : BASE<CHILD>
{

    public CHILD() : base() {}
    public override CHILD clone()
    {
        return new CHILD();
    }
}