C# 委托與事件詳解（八）

進一步檢視 MakeGreet 事件生成的代碼：

private GreetingDelegate MakeGreet; // 事件聲明實為私有委托欄位

[MethodImpl(MethodImplOptions.Synchronized)]
public void add_MakeGreet(GreetingDelegate value) {
    this.MakeGreet = (GreetingDelegate)Delegate.Combine(this.MakeGreet, value);
}
[MethodImpl(MethodImplOptions.Synchronized)]
public void remove_MakeGreet(GreetingDelegate value) {
    this.MakeGreet = (GreetingDelegate)Delegate.Remove(this.MakeGreet, value);
}

明確可見：MakeGreet 確為 GreetingDelegate 類型委托，無論聲明 public 仍編譯為 private。兩方法分別對應 += 與 -=，存取級別取決於事件聲明修飾符。

add_MakeGreet 內部調用 Delegate.Combine 將方法加入委托鏈表。委托本質是類，聲明：

public delegate void GreetingDelegate(string name);

編譯器生成：

public sealed class GreetingDelegate : System.MulticastDelegate {
    public GreetingDelegate(object @object, IntPtr method);
    public virtual IAsyncResult BeginInvoke(string name, AsyncCallback callback, object @object);
    public virtual void EndInvoke(IAsyncResult result);
    public virtual void Invoke(string name);
}

深入內容請參閱《CLR Via C#》等專書。