Web Forms :: Can't Download Song And Video

i m trying to download song and video using following code but it only save can't download it

protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
{
if (e.CommandName == "id")
{
string url = Convert.ToString(e.CommandArgument);
//Response.Redirect(url);
FileInfo fileInfo = new FileInfo(url);
Response.Clear();
Response.AddHeader("Content-Disposition", "attachment; filename=" + fileInfo.Name);
//Response.ContentType = "application/octet-stream";
Response.ContentType = "application";
Response.Flush();
}
}