private void RateDown(object obj)
 {
     SelectedSWMovie.Rating -= 0.5;
     RateDownCommand.RaiseCanExecuteChanged();
     RateUpCommand.RaiseCanExecuteChanged();
 }
 private void RateUp(object obj)
 {
     selectMovie.Rating += 1;
     RateDownCommand.RaiseCanExecuteChanged();
     RaisePropertyChanged("SelectedMovie");
 }