C#:引发事件时立即执行事件

我目前正在用C#和WPF开发一个文本到语音转换应用程序。

我添加了一个函数( speaker_finished() SpeakCompleted 播放完成或取消时调用的EventHandler。 outputVisible(false) 将某些UI元素设置为不可见。但当我重新开始播放时,我希望它们保持可见。
为了这个 outputVisible(true) 在之后被调用 speaker.SpeakAsyncCancelAll() 问题是 扬声器_完成() 在之后被调用 buttonRestart_Click() 已完成,因此为时已晚。我希望在用取消播放后立即调用它 speaker.SpeakAsyncCancelAll() 和之前 输出可见(真) 被调用。

我如何才能做到这一点?

SpeechSynthesizer speaker = new SpeechSynthesizer();

private void buttonRestart_Click(object sender, RoutedEventArgs e)
    {
        speaker.SpeakAsyncCancelAll();
        outputVisible(true);         //this function needs to be called after the function in the event handler
        speaker_Start();
    }

//function in the EventHandler of SpeakFinished
private void speaker_Finished(object sender, SpeakCompletedEventArgs e)
    {
        outputVisible(false);
    }

//function that changes the visibility
private void outputVisible(bool b)
    {
        if(b)
        {
            textBlockOutput.Visibility = Visibility.Visible;
            foreach (UIElement UIEle in GridPlaybackButtons.Children)
            {
                UIEle.Visibility = Visibility.Visible;
            }
        }
        else
        {
            textBlockOutput.Visibility = Visibility.Hidden;
            foreach (UIElement UIEle in GridPlaybackButtons.Children)
            {
                UIEle.Visibility = Visibility.Hidden;
            }
        }
    }

//function that starts the SpeechSynthesizer
private void speaker_Start()
    {
        if (speaker.State == SynthesizerState.Ready)
        {
            speaker.SpeakAsync(speakString);
        }
        else
        {
            MessageBox.Show("There already is a text being output!","Error!", MessageBoxButton.OK);
        }
    }