linq - linq“不在”查询无法解决我的期望

Question

我在Linq中编写了以下查询：

var res =  dc.TransactionLoggings
             .Where(
                x => !dc.TrsMessages(y => y.DocId != x.DocId)
              ).Select(x => x.CCHMessage).ToList();

解决以下问题：

SELECT [t0].[CCHMessage]
FROM [dbo].[TransactionLogging] AS [t0]
WHERE NOT (EXISTS(
    SELECT NULL AS [EMPTY]
    FROM [dbo].[TrsMessages] AS [t1]
    WHERE [t1].[DocId] <> [t0].[DocId]
    ))

总是返回null

我要写的Basiaclly内容如下：

Select cchmessage
from transactionlogging
where docid not in (select docid from trsmessages)

关于我的LINQ语句有什么问题的任何建议吗？

Answer 1

var res =  dc.TransactionLoggings
             .Where(tl => !dc.TrsMessages.Any(trsm=> trsm.DocId == tl.DocId))
             .Select(x => x.CCHMessage).ToList();

要么

   var trsMessagesDocId = dc.TrsMessages.Select(trsm => trsm.DocId).ToList();

   var res = dc.TransactionLoggins
                .Where(tl => !trsMessagesDocId.Contains(tl.DocId))
                .Select(tl => tl.CCHMEssage)
                .ToList();