private void AddToBookshelfList(ConcurrentBag <Volume> list, Volume volume, int bookshelfId, string bookshelfTitle)
{
Volume itemInList = list.FirstOrDefault(x => x.Id == volume.Id);
if (itemInList != null)
{
itemInList.AddToUserBookshelfs(bookshelfId, bookshelfTitle);
}
else
{
volume.AddToUserBookshelfs(bookshelfId, bookshelfTitle);
list.Add(volume);
}
}