Question

say I have a class:

abstract class A<T> {
    public abstract void foo(T a);
}

class B : A<int> {
    public void foo(int a) {              //ERROR, signature is not correct
}

How do I implement the base class in this case? The type of the parameter should be int.

Answer 1

As others have pointed out, you are missing the override keyword.

However, I want to caution you to be very careful with this pattern. You can get yourself into a world of hurt if you’re not careful:

class B<T>
{
  public virtual void M(T t) {}
  public virtual void M(int x) {}
}
class D : B<int>
{
  public override void M(int x) {}
}

Which one did it override?

No good whatsoever comes of this situation. The CLR specification recommends that you never get yourself into a situation where two method signatures unify under generic construction. Good advice, that.