case study

[tangjun]

abstract class A
{
protected int m_nWidth;
public abstract void Compute();
...
}

class B : A
{
public override void Compute()
{
... using m_m ...
}
}

class C : A
{
public override void Compute()
{
... using m_m ...
}
}

Now I need to extend class A's behavier but still need A's data structure, also needs B and C's different implementation without rewrite B and C's code.

what's the best design for the new class(s)?