想象一下我有這樣的課程：// DTOpublic class RequestrDto{    public string Name { get; set; }    public ICollection<int> CityIds { get; set; }}// ENTITY// PLACEpublic class Place{    public int Id { get; set; }    public string Name { get; set; }    public List<City> Cities { get; set; }}// CITYpublic class City{    public int Id { get; set; }    public int? PlaceId { get; set; }    public string Name { get; set; }    public string Code { get; set; }    public List<City> Cities { get; set; }    public Place Place { get; set; }}我想檢查數(shù)據(jù)庫中是否存在城市并添加到新創(chuàng)建的實(shí)體類中，該實(shí)體類將被添加到數(shù)據(jù)庫中。所以，我可以這樣做：var placeEntity = new Place() {    Name = RequestrDto.Name;}var cities = _context.Cities.Where(x => request.CityIds.Contains(x.Id)).ToList();placeEntity.Cities.AddRange(cities);如何獲取城市并檢查它們是否在數(shù)據(jù)庫中？我知道我可以通過 foreach 對其進(jìn)行迭代，但我正在尋找一種奇特的方式。