C＃事件执行顺序（Unity3D游戏）

Question

I'm developing a game in Unity (C#) and I'm relying on C# events to update the game state (ie: check whether the game is completed after a given action).

Consider the following scenario:

// model class
class A
{
    // Event definition
    public event EventHandler<EventArgs> LetterSet;
    protected virtual void OnLetterSet (EventArgs e)
    {
        var handler = LetterSet;
        if (handler != null)
            handler (this, e);
    }

    // Method (setter) that triggers the event.
    char _letter;
    public char Letter {
        get { return _letter }
        set {
            _letter = value;
            OnLetterSet (EventArgs.Empty);
        }
    }
}

// controller class
class B
{
    B ()
    {
        // instance of the model class
        a = new A();
        a.LetterSet += HandleLetterSet;
    }


    // Method that handles external (UI) events and forward them to the model class.
    public void SetLetter (char letter)
    {
        Debug.Log ("A");
        a.Letter = letter;
        Debug.Log ("C");
    }

    void HandleCellLetterSet (object sender, EventArgs e)
    {
        // check whether the constraints were met and the game is completed...
        Debug.Log ("B");
    }
}

Is it guaranteed that the output will always be ABC ? Or could the event subscriber's execution ( HandleCellLetterSet () ) be delayed until the next frame resulting in ACB ?

---

EDIT: B is the only subscriber of A.LetterSet . The question is not about execution order between multiple subscribers.

Answer 1

Yes, synchronous event handlers as shown in the post are guaranteed to finish after executing sequentially (in some order - Order of event handler execution ) before execution returns back to code that triggered event.

So your code is guaranteed to print A,B,C.

More links: are C# events synchronous? , making event asynchronous - Should I avoid 'async void' event handlers? , awaiting for asynchronous events - Asynchronous events in C# .