C＃事件执行顺序（Unity3D游戏）

Question

我在Unity（C＃）中开发游戏，我依靠C＃事件更新游戏状态（即：检查游戏是否在给定操作后完成）。

考虑以下情形：

// 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"); 
    } 
} 

是否保证输出将总是是A B C？或者事件订阅者的执行（HandleCellLetterSet()）可能会延迟到下一帧导致A C B？

---

编辑：B是A.LetterSet唯一订户。问题不在于多个订户之间的执行顺序。

Answer 1

是的，如果帖子中显示的同步事件处理程序保证在执行返回到触发事件的代码之前顺序执行（以某种顺序 - Order of event handler execution）之后完成。

所以你的代码保证打印A，B，C。

更多链接：are C# events synchronous?，使事件异步 - Should I avoid 'async void' event handlers?，等待异步事件 - Asynchronous events in C#。