var query =
from c in A
join rl in B on c.Id equals rl.ClassId into rlTemp
from rlItem in rlTemp.DefaultIfEmpty()
group rlItem.Id by new
{
c.Id,
c.Name,
c.CreateTime,
c.Remark
} into gb
select new TeachingClassStruct
{
Id = gb.Key.Id,
CreateTime = gb.Key.CreateTime,
Name = gb.Key.Name,
Remark = gb.Key.Remark,
Count = gb.Count()
};
以上linq执行结果的时候,如果出现B中没有关联A的数据情况下，最终的Count为1，查看转成的sql为
SELECT
1 AS [C1],
[GroupBy1].[K1] AS [Id],
[GroupBy1].[K2] AS [CreateTime],
[GroupBy1].[K3] AS [Name],
[GroupBy1].[K4] AS [Remark],
[GroupBy1].[A1] AS [C2]
FROM (
SELECT
[Extent1].[Id] AS [K1],
[Extent1].[CreateTime] AS [K2],
[Extent1].[Name] AS [K3],
[Extent1].[Remark] AS [K4],
COUNT(1) AS [A1]
FROM [dbo].[A] AS [Extent1]
LEFT OUTER JOIN [dbo].[B] AS [Extent2] ON [Extent1].[Id] = [Extent2].[ClassId]
WHERE ([Extent1].[IsDelete] <> 1) AND ([Extent1].[Owner] = '1019062600000109')
GROUP BY [Extent1].[Id], [Extent1].[CreateTime], [Extent1].[Name], [Extent1].[Remark]
) AS [GroupBy1]
问题处在Count（1）这个地方，如果修改linq才可以改成count（b.id）