如何在這個linq查詢中添加一個Sum（）？

Question

我期待總結「狀態」字段。

Dim _detailRecords As New DataTable 
    _detailRecords.Columns.Add("y") 
    _detailRecords.Columns.Add("z") 
    _detailRecords.Columns.Add("A", GetType(Int32)) 

    Dim workRow As DataRow 
    Dim i As Integer 

    For i = 1 To 3 
     workRow = _detailRecords.NewRow() 
     workRow(0) = i.ToString() 
     workRow(1) = "CustName" & i.ToString() 
     workRow(2) = i + 1 
     _detailRecords.Rows.Add(workRow) 
    Next 

    For i = 1 To 3 
     workRow = _detailRecords.NewRow() 
     workRow(0) = i.ToString() 
     workRow(1) = "CustName" & i.ToString() 
     workRow(2) = i + 1 
     _detailRecords.Rows.Add(workRow) 
    Next 

Dim query8 As IEnumerable(Of DataRow) = (From record As DataRow In _detailRecords _ 
    Group record By y = record.Field(Of String)("y"), _ 
        z = record.Field(Of String)("z"), _ 
        Status = record.Field(Of Int32)("Status") Into groupedRecords = Group _ 
Select groupedRecords.FirstOrDefault()) 

我也想擁有這個DataRow中的IEnumerable，因爲我將要創建的是一個DataTable與

Dim yyyyy As DataTable = query8.CopyToDataTable 

Answer 1

只需要打一個電話添加到您想要的聚合方法，且任選添加結果的別名。

Dim query = 
    From record In _detailRecords 
    Group record 
     By Y = record.Field(Of String)("y"), 
      Z = record.Field(Of String)("z"), 
      Status = record.Field(Of Int32)("Status") 
     Into groupedRecords = Group, 
      Sum(record.Field(Of Int32)("Status")) ' Get the sum of the Status values 
    Select FirstRecord = groupedRecords.FirstOrDefault, 
      Sum 

請注意，有很多方法可以編寫，這只是一種方法。