//异步事件处理器
 async void AsyncHandler(object sender, MyEventArgs args)
 {
     using (args.GetDeferral())
     {
         await Task.Delay(TimeSpan.FromSeconds(2));
     }
 }
    private async void Mr_MyEvent(object sender, MyEventArgs e)
    {
        using (e.GetDeferral())
        {
            string s = await GetString();

            e.Change = true;
        }
    }
 async void AsyncHandler(object sender, MyEventArgs args)
 {
     using IDisposable deferral = args.GetDeferral();
     await Task.Delay(TimeSpan.FromSeconds(2));
 }