How Can I Make Awaitable Event Handlers in C# for Asynchronous Data Saving Before Application Shutdown?-C++-php.cn

How Can I Make Awaitable Event Handlers in C# for Asynchronous Data Saving Before Application Shutdown?

Barbara Streisand

Release： 2025-01-08 12:46:41

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How Can I Make Awaitable Event Handlers in C# for Asynchronous Data Saving Before Application Shutdown?

Asynchronous event handler implementation in C#

Problem: Awaitable event handling

In a C# application, you may face a challenge: requiring waitable event handlers to ensure that asynchronous data saving tasks are completed before the application is closed. Currently, the synchronous nature of the event causes the game to close before the asynchronous save is completed.

Solution: Custom event delegation

The recommended approach is to create a custom event delegate that returns a Task instead of void. This way you can wait for handlers and make sure they complete before continuing.

Achievement

<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>

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Examples of usage

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

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

await game.Shutdown();</code>

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Alternative: register and call explicitly

Another option is to register callbacks and call them explicitly when needed.

<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>

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Conclusion

While asynchronous event handlers may not be the best design choice, they can be implemented in an awaitable manner using a custom event delegate or by registering and explicitly calling a callback.

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