如何通過檢查每個集合為空或不將LINQ與asp.net C＃結合使用來對嵌套集合應用LINQ查詢？

Question

如何通過將null與asp.net c＃一起使用LINQ來檢查是否為null來訪問嵌套集合？ 因為我沒有空餐計划時會得到空異常？

因為我沒有空餐計划時會得到空異常？

部分代碼：-

var hotelRoomBooking = (from n in roomsPart.DefaultIfEmpty()
                                        //where n.roomRates != null
                                        from rates in n.roomRates.DefaultIfEmpty()
                                        //where rates.roomRate != null
                                        from roomR in rates.roomRate.DefaultIfEmpty()
                                        //where roomR.mealPlans != null
                                        from mealP in roomR.mealPlans.mealPlan
                                        //where mealP.value != null
                                        from link in roomR.links.link
                                        select new
                                        {
                                            n.id,
                                            n.rooms.checkInDate,
                                            n.rooms.checkOutDate,`enter code here`
                                            n.rooms.totalCostOfRooms.totalCostInclusive.currency,
                                            roomR.averageNightlyRate.value,
                                            MealPlan = mealP.value != null ? mealP.value : string.Empty,
                                            n.stayDetails.noOfRooms,
                                            n.location.city,
                                            n.location.code
                                        }).ToList();

Answer 1

是的，您將獲得NullReferenceException。 如果要排除具有空值的行，請嘗試使用join 。