UNITY : cannot unsubscribe event handler

Question

can someone please help me with this? Here's my code:

private void Update()
{
    if (General.UpdateActive == true)
    {
        if (General.charActive == 0)
        {
            for (int i = 0; i < CharacterItem.equipmentSlots; i++)
            {
                CharacterItem.MC_EquipmentSlots[i].OnDropEvent += slot => OnDropEvent(slot);


                CharacterItem.Merc1_EquipmentSlots[i].OnDropEvent -= slot => OnDropEvent(slot);

                CharacterItem.Merc2_EquipmentSlots[i].OnDropEvent -= slot => OnDropEvent(slot);

                CharacterItem.Merc3_EquipmentSlots[i].OnDropEvent -= slot => OnDropEvent(slot);
            }
        }
        else if (General.charActive == 1)
        {
            for (int i = 0; i < CharacterItem.equipmentSlots; i++)
            {

            }
        }

For Mer1, same as above, but change MC part to -= and Merc1 part to += The problem is the event handler won't get unsubscribe when i select other character. When i select MC, it add event in MC_EquipmentSlots, and then when i select Merc1, MC_EquipmentSlots still have its event.

And the confusing part is, the code in pocket is work as intended when i cycle through the characters. I tried to copied the pocket code to equipment code, but it still gives error like I mentioned before.

CharacterItem.MC_PocketSlots[i].OnDropEvent += slot => EventHelper(slot, OnDropEvent);
CharacterItem.Merc1_PocketSlots[i].OnDropEvent -= slot => EventHelper(slot, OnDropEvent);
CharacterItem.Merc2_PocketSlots[i].OnDropEvent -= slot => EventHelper(slot, OnDropEvent);
CharacterItem.Merc3_PocketSlots[i].OnDropEvent -= slot => EventHelper(slot, OnDropEvent);

Please help and thank you in advance.

Answer 1

That happens when you use lambda expressions as event listeners! They are un-unsubscribable ;)

Rather add and remove listeners like

 CharacterItem.MC_EquipmentSlots[i].OnDropEvent += OnDropEvent;
 CharacterItem.Merc1_EquipmentSlots[i].OnDropEvent -= OnDropEvent;
 CharacterItem.Merc2_EquipmentSlots[i].OnDropEvent -= OnDropEvent;
 CharacterItem.Merc3_EquipmentSlots[i].OnDropEvent -= OnDropEvent;