Question

我有以下linq查询：

(From document In DocumentEntities
 Group Join transactionRow In TransactionEntities.Where(Function(tran) tran.PaymentType = "Charge" And tran.Amount <> 0 And (Not tran.Void.HasValue OrElse (tran.Void.HasValue AndAlso Not tran.Void.Value)))
     On document.DocumentId Equals transactionRow.DocumentId
     Into foundTransactions = Group
     From foundTransaction In foundTransactions.DefaultIfEmpty()
  Group Join documentInstrument In DocumentInstrumentEntities.Where(Function(docInst) docInst.IsPrimary)
      On document.DocumentId Equals documentInstrument.DocumentId
      Into relatedDocumentInstruments = Group
  From documentInstrument In relatedDocumentInstruments.DefaultIfEmpty()
  Join instrument In InstrumentEntities
      On documentInstrument.InstrumentId Equals instrument.InstrumentId
Where (document.DocumentId = 241083 OR document.DocumentId = 241084 OR     document.DocumentId = 241085 OR document.DocumentId = 241086 OR     document.DocumentId = 241087 OR document.DocumentId = 241090 OR     document.DocumentId = 241091 OR document.DocumentId = 241092 OR document.DocumentId = 241093 OR document.DocumentId = 241094 OR document.DocumentId = 241095 OR document.DocumentId = 241096 OR document.DocumentId = 241097 OR document.DocumentId = 241098 OR document.DocumentId = 241099 OR document.DocumentId = 241100 OR document.DocumentId = 241101 OR document.DocumentId = 241088 OR document.DocumentId = 241089)
Order By instrument.Name
Select New With
{
 .Amount = foundTransaction.Amount,
 .Code = instrument.Code,
 .Instrument = instrument.Name,
 .InstrumentId = instrument.InstrumentId,
 .Pages = document.Pages
}).GroupBy(Function(instrument) new with {instrument.Code,     instrument.Instrument})
.Select(Function(grouping) new with {.Code = grouping.Key.Code, .Instrument = grouping.Key.Instrument})

这给了我一个很好的分组的仪器和代码列表，按instrument.name排序。现在我需要知道如何访问实际分组中的项目来执行聚合功能。例如，我想在最终结果中返回SUM（金额），但我不知道如何访问每个键的实际IGrouping，以便我可以获得所需的聚合。

所以，例如，我希望我的新FINAL选择看起来像这样：

.Select(Function(grouping) new with {.Code = grouping.Key.Code, .Instrument = grouping.Key.Instrument, .Amount = SUM(grouping.amount)})

我知道在聚合函数中会有一个lambda，但我只是伪代码，所以我可以试着解释一下我的追求。

感谢您的帮助！

Answer 1

一个组是一个序列。所以，试试吧：

.Amount = grouping.Sum(Function(item) item.Amount)

Answer 2

发布的建议是正确的语法，我尝试了但是得到了异常，所以我需要在groupby之后调用.ToList（）。

以下是有效的查询：

(From document In DocumentEntities
 Group Join transactionRow In TransactionEntities.Where(Function(tran) tran.PaymentType = "Charge" And tran.Amount <> 0 And (Not tran.Void.HasValue OrElse (tran.Void.HasValue AndAlso Not tran.Void.Value)))
     On document.DocumentId Equals transactionRow.DocumentId
     Into foundTransactions = Group
     From foundTransaction In foundTransactions.DefaultIfEmpty()
  Group Join documentInstrument In DocumentInstrumentEntities.Where(Function(docInst) docInst.IsPrimary)
      On document.DocumentId Equals documentInstrument.DocumentId
      Into relatedDocumentInstruments = Group
  From documentInstrument In relatedDocumentInstruments.DefaultIfEmpty()
  Join instrument In InstrumentEntities
      On documentInstrument.InstrumentId Equals instrument.InstrumentId
Where (document.DocumentId = 241083 OR document.DocumentId = 241084 OR    document.DocumentId = 241085 OR document.DocumentId = 241086 OR document.DocumentId = 241087 OR document.DocumentId = 241090 OR document.DocumentId = 241091 OR document.DocumentId = 241092 OR document.DocumentId = 241093 OR document.DocumentId = 241094 OR document.DocumentId = 241095 OR document.DocumentId = 241096 OR document.DocumentId = 241097 OR document.DocumentId = 241098 OR document.DocumentId = 241099 OR document.DocumentId = 241100 OR document.DocumentId = 241101 OR document.DocumentId = 241088 OR document.DocumentId = 241089)
Order By instrument.Name
Select New With
{
 .Amount = foundTransaction.Amount,
 .Code = instrument.Code,
 .Instrument = instrument.Name,
 .InstrumentId = instrument.InstrumentId,
 .Pages = document.Pages
}).GroupBy(Function(instrument) new with {instrument.Code,    instrument.Instrument}).ToList().Select(Function(grouping) new with {.Code = grouping.Key.Code, .Instrument = grouping.Key.Instrument, .TotalFees= grouping.Sum(Function(item) item.Amount)}).OrderBy(Function(item) item.Instrument).ThenBy(Function(item) item.Code).ToList()

LINQ vb.net groupby在具有聚合信息的多个列上

2 个答案: