media source or if and else if, not working??

I'm making a media player that dynamically loads media files to a media element. All is well with that. Now I'm doing part where you click a button and something happens based on which media file is loaded. Here's the code:
 


void theButton_MouseLeftButtonDown(object sender, MouseButtonEventArgs
e)
{


if (theMedia.Source.ToString().Contains("intro.wmv"))
{
Do 'intro stuff'< ...