＆＃39; MIN＆＃39;不是公认的内置函数名称

Question

我有这个LINQ查询：

var gbaJoinTasksAndBatches = from gbajoin in _db.GBatchAudit
                                     join task1 in _db.TTask on gbajoin.TaskId equals task1.TaskId
                                     join batch1 in _db.TBatch on gbajoin.BatchId equals batch1.BatchId
                                     where gbajoin.EntryTime >= ReporterArgs.FromDate &&
                                           gbajoin.EntryTime <= ReporterArgs.ToDate &&
                                           gbajoin.EntryType == 1
                                     orderby gbajoin.EntryTime
                                     select new
                                     {
                                         gbajoin.EntryTime,
                                         gbajoin.BatchRunNum,
                                         task1.TaskId,
                                         task1.TaskName,
                                         batch1.BatchId,
                                         batch1.BatchName
                                     };

        var gbaGroupedByErrorMessage = from gbaJoin in gbaJoinTasksAndBatches
                                       group gbaJoin by new
                                       {
                                           gbaJoin.BatchRunNum,
                                           Task = gbaJoin.TaskName,
                                           TaskId = gbaJoin.TaskId,
                                           Batch = gbaJoin.BatchName,
                                           BatchId = gbaJoin.BatchId,
                                       } into taskBatchGroup

                                       select new TaskListDto
                                       {
                                           BatchName = taskBatchGroup.Key.Batch,
                                           BatchId = taskBatchGroup.Key.BatchId,
                                           TaskName = taskBatchGroup.Key.Task,
                                           TaskId = taskBatchGroup.Key.TaskId,
                                           BatchRunNumber = taskBatchGroup.Key.BatchRunNum,
                                           StartTime = taskBatchGroup.Min(grp => grp.EntryTime)
                                       };

        return await gbaGroupedByErrorMessage.OrderBy(t => t.StartTime).ToListAsync();

我一直收到错误＆＃34;＆＃39; MIN＆＃39;不是公认的内置函数名称。＆＃34; 但我真的不明白为什么。 我认为它在那一行的某个地方：

StartTime = taskBatchGroup.Min(grp => grp.EntryTime)

但我做想要获得该查询的最小日期时间的分组。 奇怪的是，在我将.net软件包更新到2.1.0-preview2-final之前，它实际上一直工作到昨天为止

提前致谢