从返回值的重写调用异步函数

可以创建事件处理程序

private event EventHandler LaunchFinished = delegate { };

然后订阅并在 FinishedLaunching 方法。

public override bool FinishedLaunching(UIApplication app, NSDictionary options) {
    // subscribe to event with event handler
    LaunchFinished += LaunchFinishedHandler;
    // raise event
    LaunchFinished(this, EventArgs.Empty);        
    return (true);
}

可以等待事件处理程序,这样它就不会阻塞UI线程

private async void LaunchFinishedHandler(object sender, EventArgs args) {
    LaunchFinished -= LaunchFinishedHandler; //optional

    // Setup code removed for brevity

    //On UI Thread

    await BackendService.DoSomethingAsync(); //non blocking await

    //Back on UI thread
}

事件处理程序是 async void 是允许的。使用此模式还可以捕获调用异步函数时可能出现的任何异常。

参考 Async/Await - Best Practices in Asynchronous Programming

如果你想要一个“fire and forget”异步特性,试试这个;

public static class TaskExtensions
    {
        /// <summary>       
        /// It is used when you want to call an async method without
        /// awaiting for it. Using this method suppresses the warning CS4014.
        /// </summary>
        /// <param name="task">Task to be called using a fire-and-forget call</param>
        public static void Forget(this Task task)
        {
            task.ConfigureAwait(false);
        }
    }

然后你可以用它;

YourActionName().Forget();