public ActionResult Edit(int id)
 {
     var track = _musicRepository.GetTrack(id);
     if (track == null) return HttpNotFound();
     var vm = new TrackEditViewModel(_musicRepository, track);
     return View("Edit", vm);
 }
 public ActionResult Update(Track track)
 {
     if (ModelState.IsValid)
     {
         _musicRepository.SaveTrack(track);
         return RedirectToAction("Edit", "Album", new { id = track.AlbumID });
     }
     else
     {
         var vm = new TrackEditViewModel(_musicRepository, track);
         return View("Edit", vm);
     }
 }