How to count specific column in Entity Framework Core - linq-to-sql

Question

When I use left join to perform a grouped query of two tables, the generated count statement is always count(*), I want to generate the count of the specified column. For example: count(InstrumentCode).
Framework: EF Core 3.0-preview9
var resultQuery = from t1 in query
join t2 in orgCrmQuery on t1.CUSTOMER equals t2._ID
join t3 in orgQuery on t2.NAME equals t3.ORGANIZATION_NAME into t4
from t5 in t4.DefaultIfEmpty()
join t6 in instrumentQuery on t5.ORGANIZATION_ID equals t6.ORGANIZATION_ID into t7
from t8 in t7.DefaultIfEmpty()
where t2.RECORD_TYPE == dto.RecordType && t1.MEETING_NO == dto.MeetingNo
group t8.INSTRUMENT_CODE by new {
t1.PERSON_NAME,
t1.SEX,
t1.POSTION,
t1.PHONE,
t1.IS_CIZHU_KEHU,
t2.NAME,
t2.ORG_LEVEL,
} into g
orderby g.Key.NAME
select new {
g.Key.PERSON_NAME,
g.Key.SEX,
g.Key.POSTION,
g.Key.PHONE,
g.Key.IS_CIZHU_KEHU,
g.Key.NAME,
g.Key.ORG_LEVEL,
INSTRUMENT_COUNT = g.Count()
};
SQL statement generated：
SELECT
[t].[PERSON_NAME],
[t].[SEX],
[t].[POSTION],
[t].[PHONE],
[t].[IS_CIZHU_KEHU],
[t0].[NAME],
[t0].[ORG_LEVEL],
COUNT ( * ) AS [INSTRUMENT_COUNT]
FROM
[dbo].[TB_MEETING_PERSONAL] AS [t] WITH ( NOLOCK )
INNER JOIN [dbo].[TB_ORG_CRM] AS [t0] WITH ( NOLOCK ) ON [t].[CUSTOMER] = [t0].[_ID]
LEFT JOIN [dbo].[MS_ORGANIZATION] AS [m] WITH ( NOLOCK ) ON [t0].[NAME] = [m].[ORGANIZATION_NAME]
LEFT JOIN [dbo].[MS_INSTRUMENT] AS [m0] WITH ( NOLOCK ) ON [m].[ORGANIZATION_ID] = [m0].[ORGANIZATION_ID]
WHERE
(
( ( [t0].[RECORD_TYPE] = #__dto_RecordType_0 ) AND ( [t0].[RECORD_TYPE] IS NOT NULL AND #__dto_RecordType_0 IS NOT NULL ) )
OR ( [t0].[RECORD_TYPE] IS NULL AND #__dto_RecordType_0 IS NULL )
)
AND (
( ( [t].[MEETING_NO] = #__dto_MeetingNo_1 ) AND ( [t].[MEETING_NO] IS NOT NULL AND #__dto_MeetingNo_1 IS NOT NULL ) )
OR ( [t].[MEETING_NO] IS NULL AND #__dto_MeetingNo_1 IS NULL )
)
GROUP BY
[t].[PERSON_NAME],
[t].[SEX],
[t].[POSTION],
[t].[PHONE],
[t].[IS_CIZHU_KEHU],
[t0].[NAME],
[t0].[ORG_LEVEL]
ORDER BY
[t0].[NAME] OFFSET 0 ROWS FETCH NEXT 100 ROWS ONLY
I checked some information, but I didn't find a solution.

Answer 1

Based on your linq, same result for .Count(INSTRUMENT_COUNT) and .Count(*) or .Count(1) because this will return the # of rows regardless of the value of your INSTRUMENT_COUNT.
But if you want to get count specifically for INSTRUMENT_COUNT you can try this.
var resultQuery = from t1 in query
join t2 in orgCrmQuery on t1.CUSTOMER equals t2._ID
join t3 in orgQuery on t2.NAME equals t3.ORGANIZATION_NAME into t4
from t5 in t4.DefaultIfEmpty()
join t6 in instrumentQuery on t5.ORGANIZATION_ID equals t6.ORGANIZATION_ID into t7
from t8 in t7.DefaultIfEmpty()
where t2.RECORD_TYPE == dto.RecordType && t1.MEETING_NO == dto.MeetingNo
group t8.INSTRUMENT_CODE by new {
t1.PERSON_NAME,
t1.SEX,
t1.POSTION,
t1.PHONE,
t1.IS_CIZHU_KEHU,
t2.NAME,
t2.ORG_LEVEL,
t8.INSTRUMENT_CODE,
} into g
orderby g.Key.NAME
select new {
g.Key.PERSON_NAME,
g.Key.SEX,
g.Key.POSTION,
g.Key.PHONE,
g.Key.IS_CIZHU_KEHU,
g.Key.NAME,
g.Key.ORG_LEVEL,
INSTRUMENT_COUNT = g.Select(x => x.INSTRUMENT_CODE).Distinct().Count()
};