问SpeechSynthesizer中的持续内存泄漏

EN

<Window x:Class="SpeechTest.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Window1" Height="300" Width="300">
<Grid>
    <StackPanel Orientation="Vertical">

        <Button Content="Start Speaking" Click="Start_Click" Margin="10" />
        <Button Content="Stop Speaking" Click="Stop_Click" Margin="10" />
        <Button Content="Exit" Click="Exit_Click" Margin="10"/>

    </StackPanel>
</Grid>

// Start of code behind
using System;
using System.Windows;
using System.Speech.Synthesis;

namespace SpeechTest
{
    public partial class Window1 : Window
    {

        // speak setting
        private bool speakingOn = false;
        private int curLine = 0;
        private string [] speakLines = {
            "I am wondering",
            "Why whenever Speech is called",
            "A memory leak occurs",
            "If you run this long enough",
            "It will eventually crash",
            "Any help would be appreciated" };

        public Window1()
        {
            InitializeComponent();
        }

        private void Start_Click(object sender, RoutedEventArgs e)
        {
            speakingOn = true;
            SpeakLine();
        }

        private void Stop_Click(object sender, RoutedEventArgs e)
        {
            speakingOn = false;
        }

        private void Exit_Click(object sender, RoutedEventArgs e)
        {
            App.Current.Shutdown();
        }

        private void SpeakLine()
        {
            if (speakingOn)
            {
                // Create our speak object
                SpeechSynthesizer spk = new SpeechSynthesizer();
                spk.SpeakCompleted += new EventHandler(spk_Completed);
                // Speak the line
                spk.SpeakAsync(speakLines[curLine]);
            }
        }

        public void spk_Completed(object sender, SpeakCompletedEventArgs e)
        {
            if (sender is SpeechSynthesizer)
            {

                // get access to our Speech object
                SpeechSynthesizer spk = (SpeechSynthesizer)sender;
                // Clean up after speaking (thinking the event handler is causing the memory leak)
                spk.SpeakCompleted -= new EventHandler(spk_Completed);
                // Dispose the speech object
                spk.Dispose();
                // bump it
                curLine++;
                // check validity
                if (curLine >= speakLines.Length)
                {
                    // back to the beginning
                    curLine = 0;
                }
                // Speak line
                SpeakLine();
            }
        }
    }
}