why cant i click a button in unity code example

Example: how to code button click unity

using UnityEngine;
using UnityEngine.UI;
using System.Collections;
public class ClickExample : MonoBehaviour {
	public Button yourButton;	
    
    void Start () {
		Button btn = yourButton.GetComponent<Button>();
		btn.onClick.AddListener(TaskOnClick);
	}	
    void TaskOnClick(){
		Debug.Log ("You have clicked the button!");
	}
}