LINQ Group通過多表Inner Join和聚合函數

Question

我有以下Linq到EF查詢：

from envelope in ENVELOPEs.AsNoTracking()
join spool in SPOOLs.AsNoTracking() on envelope.SPOOL_ID equals spool.SPOOL_ID
join extract in EXTRACTs.AsNoTracking() on spool.EXTRACT_ID equals extract.EXTRACT_ID
join extractProfile in EXTRACT_PROFILE.AsNoTracking() on extract.EXTRACT_PROFILE_ID equals extractProfile.EXTRACT_PROFILE_ID
join box in BOXes.AsNoTracking() on envelope.BOX_ID equals box.BOX_ID
join pallet in PALLETs.AsNoTracking() on box.PALLET_ID equals pallet.PALLET_ID
join fakeCap in FAKECAPs.AsNoTracking() on envelope.FAKECAP_ID equals fakeCap.FAKECAP_ID
join envWeightRange in ENVELOPE_WEIGHT_RANGE.AsNoTracking() on envelope.ENV_WEIGHT_RANGE_ID equals envWeightRange.ENV_WEIGHT_RANGE_ID
join ptype in PTYPEs.AsNoTracking() on spool.PTYPE_ID equals ptype.PTYPE_ID
join envType in ENVTYPEs.AsNoTracking() on ptype.ENVTYPE_ID equals envType.ENVTYPE_ID
join boxType in BOXTYPEs.AsNoTracking() on envType.BOXTYPE_ID equals boxType.BOXTYPE_ID
where spool.JSHEET_ID == 8
orderby envWeightRange.ENV_WEIGHT_RANGE_CODE,
    fakeCap.FAKECAP_DEST_TARIF
group new { envelope, envType } by
new 
{ 
    fakeCap.FAKECAP_DEST_TARIF,
    envWeightRange.ENV_WEIGHT_RANGE_CODE    
} into grouped
select new
{
    FAKECAP_DEST_TARIF = grouped.Key.FAKECAP_DEST_TARIF,
    ENV_WEIGHT_RANGE_CODE = grouped.Key.ENV_WEIGHT_RANGE_CODE,
    ENVTYPE_COD_OMOLOG = grouped.Max(item => item.ENVTYPE_COD_OMOLOG), // Error: ENVTYPE_COD_OMOLOG not defined
    TOTALE_BUSTE = grouped.Count()
}

它沒有說未定義提交的ENVTYPE_COD_OMOLOG。 （對不起，我本來希望在那里粘貼整個異常，但它不是對操作系統區域設置的不理解）。

但是，如果我在組中包含字段ENVTYPE_COD_OMOLOG而不使用聚合函數訪問它，則它可以完美地工作：

from envelope in ENVELOPEs.AsNoTracking()
join spool in SPOOLs.AsNoTracking() on envelope.SPOOL_ID equals spool.SPOOL_ID
join extract in EXTRACTs.AsNoTracking() on spool.EXTRACT_ID equals extract.EXTRACT_ID
join extractProfile in EXTRACT_PROFILE.AsNoTracking() on extract.EXTRACT_PROFILE_ID equals extractProfile.EXTRACT_PROFILE_ID
join box in BOXes.AsNoTracking() on envelope.BOX_ID equals box.BOX_ID
join pallet in PALLETs.AsNoTracking() on box.PALLET_ID equals pallet.PALLET_ID
join fakeCap in FAKECAPs.AsNoTracking() on envelope.FAKECAP_ID equals fakeCap.FAKECAP_ID
join envWeightRange in ENVELOPE_WEIGHT_RANGE.AsNoTracking() on envelope.ENV_WEIGHT_RANGE_ID equals envWeightRange.ENV_WEIGHT_RANGE_ID
join ptype in PTYPEs.AsNoTracking() on spool.PTYPE_ID equals ptype.PTYPE_ID
join envType in ENVTYPEs.AsNoTracking() on ptype.ENVTYPE_ID equals envType.ENVTYPE_ID
join boxType in BOXTYPEs.AsNoTracking() on envType.BOXTYPE_ID equals boxType.BOXTYPE_ID
where spool.JSHEET_ID == 8
orderby envWeightRange.ENV_WEIGHT_RANGE_CODE,
    fakeCap.FAKECAP_DEST_TARIF
group new { envelope, envType } by
new 
{ 
    fakeCap.FAKECAP_DEST_TARIF,
    envWeightRange.ENV_WEIGHT_RANGE_CODE,
    envType.ENVTYPE_COD_OMOLOG
} into grouped
select new
{
    FAKECAP_DEST_TARIF = grouped.Key.FAKECAP_DEST_TARIF,
    ENV_WEIGHT_RANGE_CODE = grouped.Key.ENV_WEIGHT_RANGE_CODE,
    ENVTYPE_COD_OMOLOG = grouped.Key.ENVTYPE_COD_OMOLOG,
    TOTALE_BUSTE = grouped.Count()
}

Answer 1

在該查詢中， grouped是IGrouping<TKey,T> ，其中：

• T是投影類型，在這種情況下是new { envelope, envType }

• TKey是分組鍵，在這種情況下（不包括ENVTYPE_COD_OMOLOG ）：

   new { fakeCap.FAKECAP_DEST_TARIF, envWeightRange.ENV_WEIGHT_RANGE_CODE } 

除了具有屬性TKey Key之外IGrouping<TKey,T>也可以被視為IEnumerable<T> 。 這意味着從每個組中獲取最大ENVTYPE_COD_OMOLOG ，您需要以下列方式更改您的選擇（ Max將應用於T的序列）：

select new
{
    FAKECAP_DEST_TARIF = grouped.Key.FAKECAP_DEST_TARIF,
    ENV_WEIGHT_RANGE_CODE = grouped.Key.ENV_WEIGHT_RANGE_CODE,
    ENVTYPE_COD_OMOLOG = grouped.Max(item => item.envType.ENVTYPE_COD_OMOLOG),
    TOTALE_BUSTE = grouped.Count()
}

這樣您就不需要按ENVTYPE_COD_OMOLOG分組，並且仍然可以在結果中獲得每組的最大值。