如何在 C# 中建立可等待事件處理程序，以便在應用程式關閉之前非同步保存資料？

<code class="language-csharp">class Game
{
    public event Func<object, EventArgs, Task> GameShuttingDown;

    public async Task Shutdown()
    {
        Func<object, EventArgs, Task> handler = GameShuttingDown;

        if (handler == null) return;

        Delegate[] invocationList = handler.GetInvocationList();
        Task[] handlerTasks = new Task[invocationList.Length];

        for (int i = 0; i < invocationList.Length; i++)
        {
            handlerTasks[i] = ((Func<object, EventArgs, Task>)invocationList[i])(this, EventArgs.Empty);
        }

        await Task.WhenAll(handlerTasks);
    }
}</code>

<code class="language-csharp">Game game = new Game();

game.GameShuttingDown += async (sender, args) => await SaveUserData();

await game.Shutdown();</code>

<code class="language-csharp">class Game
{
    private List<Func<Task>> _shutdownCallbacks = new List<Func<Task>>();

    public void RegisterShutdownCallback(Func<Task> callback)
    {
        _shutdownCallbacks.Add(callback);
    }

    public async Task Shutdown()
    {
        var callbackTasks = new List<Task>();

        foreach (var callback in _shutdownCallbacks)
        {
            callbackTasks.Add(callback());
        }

        await Task.WhenAll(callbackTasks);
    }
}</code>