How to show waiting Image in WPF Application?

<grid>
<mediaelement x:name="MediaPlayer" mediaended="MediaPlayer_MediaEnded" unloadedbehavior="Manual" loadedbehavior="Manual" visibility="Collapsed"
="" height="81" horizontalalignment="Left" margin="199,108,0,0" verticalalignment="Top" width="91">
<Button Content="Button" Height="23" HorizontalAlignment="Left" Margin="118,94,0,0" Name="button1" VerticalAlignment="Top" Width="75" KeyDown="button1_KeyDown" Click="button1_Click"/>



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private void button1_Click(object sender, RoutedEventArgs e)
{
try
{
MediaPlayer_MediaEnded(sender, e);

System.Threading.Thread.Sleep(5000); // Added for testing purpose
}
finally
{

MediaPlayer.Stop();
MediaPlayer.Visibility = Visibility.Collapsed;
}
}

private void MediaPlayer_MediaEnded(object sender, RoutedEventArgs e)
{
MediaPlayer.Visibility = Visibility.Visible;
MediaPlayer.Source = new Uri(@"/Images/ABC_busy_animation.gif");
MediaPlayer.Position = new TimeSpan(0, 0, 2);
MediaPlayer.Play();
}

it won't work while thread is sleeping and finally it will collapsed without showing any effect.