GetComponent( ) and Polymorphism

I have a EnemyGrunt class that inherits Enemy class. I’m trying to call a method from the Enemy class like this, when casting the overlap on a game object with the EnemyGrunt script:

numberOfLayersDetected = Physics2D.OverlapBoxNonAlloc(meleeAttackSpawnSpot.position, 
                new Vector2(meleeAttackBoxRadiusX, meleeAttackBoxRadiusY), 0, castResults, 1 << LayerMask.NameToLayer("Enemy"));

            if (numberOfLayersDetected > 0) {
                for (int i = 0; i < castResults.Length; i++) {
                    Enemy currentEnemy = castResults*.gameObject.GetComponent<Enemy>();*

However, the currentEnemy variable doesn’t receive anything from the GetComponent(). Probably I’m doing something wrong, so I ask you: how can I inflict damage in any type of object that inherits from Enemy class?

GetComponent works with polymorphism, so the problem must be somewhere else.

Are you sure your EnemyGrunt script is placed on the same object as his collider? Are you sure you are even getting expected results from your OverlapBox?