在查看下面的代码时，我无法找出this.AddRange（hoteltasks）;在第21行。
我想知道AddRange方法将hoteltasks的元素添加到哪个集合。

public class HotelViewModel : ObservableRangeCollection<RoomViewModel>, INotifyPropertyChanged
{
    // It's a backup variable for storing TaskViewModel objects
    private ObservableRangeCollection<RoomViewModel> hoteltasks = new ObservableRangeCollection<RoomViewModel>();

    public HotelViewModel()
    {
    }

    public HotelViewModel(Hotel hotel, bool expanded = false)
    {
        this.Hotel = hotel;
        this._expanded = expanded;

        foreach (Room task in hotel.Tasks)
        {
            hoteltasks.Add(new RoomViewModel(task));
        }
        if (expanded)
            this.AddRange(hoteltasks);
    }
 
    private bool _expanded;
    public bool Expanded
    {
        get { return _expanded; }
        set
        {
            if (_expanded != value)
            {
                _expanded = value;
                OnPropertyChanged(new PropertyChangedEventArgs("Expanded"));
                  
                if (_expanded)
                {
                    this.AddRange(hoteltasks);
                }
                else
                {
                    this.Clear();
                }
            }
        }
    }
}