將LINQ查詢放入以屬性為引數的方法中

我不知道如何在標題中解釋，所以我盡可能詳細地描述了我的擔憂：

我有一個具有不同屬性的物件串列，我通過一個名為“OriginID”的屬性和一個 LINQ 查詢對它們進行分組，以獲得不同屬性（NetTotal 和 ShippingCost）的總和。

由于我有多個屬性要獲得總和，因此我現在需要為每個組元素復制 LINQ 查詢（我有更多欄位，例如“OriginID”，例如 CountryID 等等。

Dim ListA = SalesTurnoverResult.GroupBy(
    Function(x) x.OriginID).Select(
    Function(a) New With {
        Key .OriginID = a.Key,
        Key .sum_a = a.Sum(Function(s) s.NetTotal),
        Key .sum_b = a.Sum(Function(s) s.ShippingCost)})

我想將“一個”查詢封裝到一個函式中，其中組（即物件的屬性）可以作為引數給出，如下所示：

Public SubGetGroupedSummary(NameOfProperty As .... [the property])
    Dim ListA = SalesTurnoverResult.GroupBy(
        Function(x) x.[NameOfProperty]).Select(
        Function(a) New With {
            Key .OriginID = a.Key,
            Key .sum_a = a.Sum(Function(s) s.NetTotal),
            Key .sum_b = a.Sum(Function(s) s.ShippingCost)})
End Sub

甚至有可能這樣做嗎？

我添加了更多細節：

Public SalesTurnoverResult As List(Of SummaryClass)

'The (Sample)Class
Public Class SummaryClass
    Public Property NetTotal As Single'Sum
    Public Property ShippingCost As Single'Sum

    Public Property InvoiceCountry As Integer'Group
    Public Property OriginID As Single'Group
End Class

uj5u.com熱心網友回復：

一個簡單的解決方案是包含一個選擇案例：

ListA = SalesTurnoverResult.GroupBy(
    Function(x)
        Select Case NameOfProperty
            Case "OriginID" : Return x.OriginID
            Case "InvoiceCountry" : Return x.InvoiceCountry
        End Select
    End Function
    ).Select(
    Function(a) New With {
    Key .OriginID = a.Key,
    Key .sum_a = a.Sum(Function(s) s.NetTotal),
    Key .sum_b = a.Sum(Function(s) s.ShippingCost)})

編輯＃1：

這是我嘗試過的：

  ....
    With SalesTurnoverResult
        Dim sc As New SummaryClass
        sc.NetTotal = 100 : sc.ShippingCost = 20 : sc.InvoiceCountry = 1 : sc.OriginID = 1000 : sc.Str = "abc"
        .Add(sc)
        sc = New SummaryClass
        sc.NetTotal = 50 : sc.ShippingCost = 25 : sc.InvoiceCountry = 1 : sc.OriginID = 1001 : sc.Str = "efg"
        .Add(sc)
        sc = New SummaryClass
        sc.NetTotal = 120 : sc.ShippingCost = 25 : sc.InvoiceCountry = 2 : sc.OriginID = 1002 : sc.Str = "jkl"
        .Add(sc)
        sc = New SummaryClass
        sc.NetTotal = 50 : sc.ShippingCost = 20 : sc.InvoiceCountry = 3 : sc.OriginID = 1001 : sc.Str = "abc"
        .Add(sc)
    End With
    GetGroupedSummaryStrictON("OriginID")
    GetGroupedSummaryStrictON("InvoiceCountry")
    GetGroupedSummaryStrictON("Str")
   ....
   ....

Public Sub GetGroupedSummaryStrictON(NameOfProperty As String)
    Try
        Dim ListA = SalesTurnoverResult.GroupBy(
        Function(x) As Object
            Select Case NameOfProperty
                Case "OriginID" : Return CSng(x.OriginID)
                Case "InvoiceCountry" : Return CInt(x.InvoiceCountry)
                Case Else  ' x.Str
            End Select
            Return CType(x.Str, String)
        End Function).Select(
            Function(a) New With {
            Key .OriginID = a.Key,
            Key .sum_a = a.Sum(Function(s) s.NetTotal),
            Key .sum_b = a.Sum(Function(s) s.ShippingCost)}).ToArray

        Console.WriteLine(NameOfProperty)
        For Each a In ListA
            Console.WriteLine(String.Format("{0} {1} {2}", a.OriginID, a.sum_a, a.sum_b))
        Next
        Console.WriteLine("--------------------")

    Catch ex As Exception
    End Try
End Sub

輸出：

標籤：VB.net 林克

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