MediaElement 和 thread.sleep 的问题

Question

I am making a selection change from a combobox. When that event occurs, I want to play one media file, pause 5 seconds and then play another media file. What is actually happening is that there is a 5 second pause. Then only the second media file plays (vb.mp4). What am I doing wrong here?

private void cmb_adGroupZoneOne_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
       this.mediaElement.Source = new Uri("C:/fb.mp4");
       this.mediaElement.LoadedBehavior = MediaState.Manual;
       this.mediaElement.Play();

       System.Threading.Thread.Sleep(5000);

       this.mediaElement.Source = new Uri("C:/vb.mp4");
       this.mediaElement.LoadedBehavior = MediaState.Manual;
       this.mediaElement.Play();
    }

Answer 1

<MediaElement Name="mediaElement" MediaEnded="mediaElement_MediaEnded"  />

private void cmb_adGroupZoneOne_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
       this.mediaElement.Source = new Uri("C:/fb.mp4");
       this.mediaElement.LoadedBehavior = MediaState.Manual;
       this.mediaElement.Play();

    }


private void mediaElement_MediaEnded(object sender, RoutedEventArgs e)
{

       System.Threading.Thread.Sleep(5000);

       this.mediaElement.Source = new Uri("C:/vb.mp4");
       this.mediaElement.LoadedBehavior = MediaState.Manual;
       this.mediaElement.Play();  
}