UIUtility.cs

using System;
using System.Collections;
using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;

public static class UIUtility
{
    public static EventTrigger.TriggerEvent AddEvent(this GameObject o,EventTriggerType e)
    {
        var trigger = o.GetComponent<EventTrigger>() ?? o.AddComponent<EventTrigger>();
        var entry = new EventTrigger.Entry();
        entry.eventID = EventTriggerType.PointerClick;
        trigger.triggers.Add(entry);
        return entry.callback;
    }

    public static void RemoveEvent(this GameObject o,EventTriggerType e)
    {
        var trigger = o.GetComponent<EventTrigger>() ?? o.AddComponent<EventTrigger>();
        trigger.triggers.Remove(new EventTrigger.Entry {eventID = e});
    }
}