Getting files are being used by other process while playing

I am displaying video files from a local folder creating a playlist and passing them to embed windows media player.I am starting the display by button click even.how to clear the playlist from media player.when i again click on button i am getting error as file is being used by other process.

 

aspx code

 

 

button event

 

protected void btnsubmit_Click(object sender, EventArgs e)

{

string urlstr = Server.MapPath("~/bin") + "\\Images\\Playlist1.wpl";

Clearplaylist();

embed1.Attributes.Remove(urlstr);

embed1.Attributes.Add("src", urlstr); // here i am passing the playlist for playing

}

 

how to dispose the files or release them for further being used