c# - MediaElement playlist doesn't works

Question

I'm trying to do a TTS app for Windows Phone, but i have a little problem. I'v make a function to call Google TTS service and play it on a MediaElement, that works perfect.

That's the function i'v wrote

        public void Say(string phrase)
    {
        mediaElement1.Source = new Uri("http://translate.google.com/translate_tts?tl=en&q=" + phrase, UriKind.Absolute));
        mediaElement1.Play();
    }

But if i call the function a lot of times, for example, in a for loop, it just say the last item of loop. For example

for (int i = 0; i < 10; i++)
{
  Say(Convert.ToString(i));
}

Then it just say 'Nine', nope '1,2,3,4,...'

I'v tried to do a 'Playlist' of words, that the function will play. This is my code.

 bool first = true;
    List<Uri> uriTask = new List<Uri>();
    public void Say(string phrase)
    {
        uriTask.Add(new Uri("http://translate.google.com/translate_tts?tl=es&q=" + phrase, UriKind.Absolute));
        if (mediaElement1.CurrentState != MediaElementState.Playing)
        {
            if (first)
            {
                CHECK();
                first = false;
            }
            else
            {
                mediaElement1.MediaEnded += delegate
                {
                    mediaElement1.Position = TimeSpan.Zero;
                    CHECK();
                };

            }
        }
    }




    private void CHECK()
    {
        if (uriTask.Count > 0)
        {
            mediaElement1.Source = uriTask[0];
            mediaElement1.Play();
            uriTask.RemoveAt(0);
        }
    }

Thanks. Greetings