Question

If a class fires events in its methods, the class does not have to know what or who subscribes its events. It is not also important if there is any subscriber.

In the code below, if there is not any subscriber to OnTrigger event, an exception occures.

public class EventTrigger
{
    public static void Main(string[] args)
    {
        (new EventTrigger()).Trigger();
    }

    public delegate void Delegate1();
    public event Delegate1 OnTrigger;

    void Trigger()
    {
        OnTrigger();
    }
}

I can call the event like this;

if (OnTrigger != null)
{
    OnTrigger();
}

But it seems weird to me, because the triggerer does not have to know about subscription.

My question is:

Do I have to check if the event reference is null whenever I use it.

Answer 1

If you initialize OnTrigger then you wont have to do the check.
e.g.

public event Action OnTrigger = delegate { };

---

Yes ´delegate { }´ instantiates a new object, which is why this allows you to omit the ´null´ check.

´delegate { }´ returns nothing, so if you want it to return a string (which you need if Delegate1 returns a string) then you simply add ´return “”;´ e.g.:

public event Action OnTrigger = delegate { return string.Empty; };

One I should add is that it’s bad practice to do this in order to avoid a null check, as it’s a lazy mans hack. Some code can still set the event to null, ´OnTrigger = null´ will break your code. And when it comes to (de)serialization it wont work at all.