我应该避免“async void"事件处理程序吗? [英] Should I avoid 'async void' event handlers?

问题描述

我知道使用即发即弃 async void 方法来启动任务通常被认为是一个坏主意，因为没有挂起任务的跟踪并且处理异常很棘手可能会被抛出到这样的方法中.

I know it is considered generally a bad idea to use fire-and-forget async void methods to start tasks, because there is no track of the pending task and it is tricky to handle exceptions which might be thrown inside such a method.

通常我应该避免使用 async void 事件处理程序吗? 例如，

Should I generally avoid async void event handlers, as well? For example,

private async void Form_Load(object sender, System.EventArgs e)
{
        await Task.Delay(2000); // do async work
        // ...
} 

我可以这样重写:

Task onFormLoadTask = null; // track the task, can implement cancellation

private void Form_Load(object sender, System.EventArgs e)
{
        this.onFormLoadTask = OnFormLoadTaskAsync(sender, e);
} 

private async Task OnFormLoadTaskAsync(object sender, System.EventArgs e)
{
        await Task.Delay(2000); // do async work
        // ...
} 

除了可能的重入之外，异步事件处理程序的水下岩石是什么?

推荐答案

准则是在事件处理程序中使用时避免async void except，因此使用async void 在事件处理程序中是可以的.

The guideline is to avoid async void except when used in an event handler, so using async void in an event handler is OK.

也就是说，出于单元测试的原因，我经常喜欢分解所有async void方法的逻辑.例如，

That said, for unit testing reasons I often like to factor out the logic of all async void methods. E.g.,

public async Task OnFormLoadAsync(object sender, EventArgs e)
{
  await Task.Delay(2000);
  ...
}

private async void Form_Load(object sender, EventArgs e)
{
  await OnFormLoadAsync(sender, e);
}

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