SL17: Providing Static Alternative Content for Silverlight Media Playing in a MediaElement

<UserControl x:Class="ReplaceAudioWithTranscriptText.MainPage"
   xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
   xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
   xmlns:sys="clr-namespace:System;assembly=mscorlib">
   <UserControl.Resources>
       <sys:String x:Key="transSpeakerName">Matt Raymond: </sys:String>
       <sys:String x:Key="transText">This is Matt Raymond at the Library of Congress.
Each year thousands of book lovers of all ages visit the nation's capital to celebrate the joys 
of reading and lifelong literacy, at the Library of Congress National Book Festival. 
For the first time in the festival's nine year history, President Barack Obama and 
First Lady Michelle Obama will serve as honorary chairs of this free event. </sys:String>
   </UserControl.Resources>
   <StackPanel x:Name="LayoutRoot" Background="White" >
       <TextBlock FontSize="30" Foreground="Blue">Library of Congress Audio</TextBlock>
       <MediaElement Source="/locintro.wma" AutoPlay="False" Name="player" Height="0" />
       <StackPanel Orientation="Horizontal" Name="ControlBar">
           <Button Name="Play" Click="Play_Click">Play</Button>
           <Button Name="Stop" Click="Stop_Click">Stop</Button>
           <Button Name="TextAlt" Click="TextAlt_Click">Display Transcript</Button>
       </StackPanel>
   </StackPanel>
</UserControl>

   public partial class MainPage : UserControl
   {
       RichTextBox rtb;
       bool transDisplayed=false;
       public MainPage()
       {
           InitializeComponent();
           rtb = new RichTextBox();
           rtb.IsReadOnly = true;
           Paragraph p = new Paragraph();
           Run speakerName = new Run();
           speakerName.Text = this.Resources["transSpeakerName"] as String;
           speakerName.FontWeight = FontWeights.Bold;
           Run transText = new Run();
           transText.Text = this.Resources["transText"] as String;
           p.Inlines.Add(speakerName);
           p.Inlines.Add(transText);
           rtb.Blocks.Add(p);
       }
       private void Play_Click(object sender, RoutedEventArgs e)
       {
           player.Play();
           Play.IsEnabled = false;
       }
       private void Stop_Click(object sender, RoutedEventArgs e)
       {
           player.Stop();
           Play.IsEnabled = true;
       }
       private void TextAlt_Click(object sender, RoutedEventArgs e)
       {
           Panel parent = (player.Parent as Panel);
           if (!transDisplayed)
           {
               DisplayTranscript();
               (sender as Button).Content = "Hide Transcript";
               transDisplayed = true;
           }
           else
           {
               parent.Children.Remove(rtb);
               (sender as Button).Content = "Display Transcript";
               transDisplayed = false;
           }
       }
       private void DisplayTranscript()
       {
           Panel parent = (player.Parent as Panel);
           parent.Children.Add(rtb);
       }