// checks the database which chalets are occupied in the specified period and returns a list of available chalets public static List <int> AvailableChalets(DateTime arrivalDate, DateTime departureDate, int chaletId) { List <int> availableChalets = new List <int> { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; if (DatabaseCalls.OccupiedChalets(arrivalDate, departureDate, chaletId) != null) { foreach (int item in DatabaseCalls.OccupiedChalets(arrivalDate, departureDate, chaletId)) { availableChalets.Remove(item); } } return(availableChalets); }