Linq左连接查询时，结果为空报错误Nullableobjectmusthaveavalue的解决方法

Z时代
2024-01-10
分类：综合

左连接查询结果除了主表字段不为空，其他的都有可能为空，可使用三元运算符代替Null值：

 var TableNamelist = ctx.UWipprocconfset.Where(t => t.Factory == sFactory && t.AppliedEngineType == sAppliedEngineType && t.DeactiveFlag != "Y")
                          .Join(
                          ctx.UWipprocconfsetitemrel.Where(t => t.Oper == sOper),
                          a => new { f = a.Factory, id = a.SetId },
                          b => new { f = b.Factory, id = b.SetId },
                          (a, b) => new
                          {
                              b.SeqNum,
                              b.ItemId,
                              b.Factory
                          }).Join(
                          ctx.UWipprocconfitem.Where(t => t.ActivityType == "P"),
                          a => new { f = a.Factory, id = a.ItemId },
                          b => new { f = b.Factory, id = b.ItemId },
                          (a, b) => new { a.SeqNum, BB = b }
                          ).GroupJoin(
                        ctx.UWipprocconfsts.Where(t => t.EngineNo == sEngineNo),
                        a => new { f = a.BB.Factory, id = a.BB.ItemId },
                        b => new { f = b.Factory, id = b.ItemId },
                        (a, b) => new { AAA = a, BBB = b })
                        .SelectMany(
                        ab => ab.BBB.DefaultIfEmpty(),//Left Join
                        (a, b) => new
                        {
                            a.AAA.SeqNum,
                            a.AAA.BB.ActivityDesc,
                            a.AAA.BB.ItemId,
                            Factory = b.Factory == null ? " " : b.Factory,
                            EngineNo = b.EngineNo == null ? " " : b.EngineNo,
                            Oper = b.Oper == null ? " " : b.Oper,
                            Step = b.Step == null ? " " : b.Step,
                            ActivityType = b.ActivityType == null ? " " : b.ActivityType,
                            Shift = b.Shift == null ? " " : b.Shift,
                            NoOfWorker = b.NoOfWorker == null ? 0 : b.NoOfWorker,
                            Workers = b.Workers == null ? " " : b.Workers,
                            ActualStartDate = b.ActualStartDate == null ? " " : b.ActualStartDate,
                            ActualEndDate = b.ActualEndDate == null ? " " : b.ActualEndDate,
                            IssueFlag = b.IssueFlag == null ? " " : b.IssueFlag,
                            DelayFlag = b.DelayFlag == null ? " " : b.DelayFlag,
                            Remark = b.Remark == null ? " " : b.Remark,
                            CreateUserId = b.CreateUserId == null ? " " : b.CreateUserId,
                            CreateTime = b.CreateTime == null ? " " : b.CreateTime,
                            UpdateUserId = b.UpdateUserId == null ? " " : b.UpdateUserId,
                            UpdateTime = b.UpdateTime == null ? " " : b.UpdateTime                        }).ToList();