How do i make my enemy attack my player?

I have been trying to make my enemy do damage to my player within a certain distance of them but its not working. My script is right here.

void OnCollisionEnter (Collider other) { var Dmg = GetComponent (); if (other.gameObject.CompareTag ("Player")) { Dmg.TakeDamage (1); } }

can you tell me whats wrong with it? thx!