onCollisionEnter2D not getting button enter code example

Example 1: oncollisionenter2d

using UnityEngine;
using System.Collections;public class ExampleClass : MonoBehaviour {
    void OnCollisionEnter2D(Collision2D coll) {
        if (coll.gameObject.tag == "Enemy")
            coll.gameObject.SendMessage("ApplyDamage", 10);
        
    }
}

Example 2: oncollisionenter2d

OnCollisionEnter2D(Collision2D Collider)