vb.net - Linq to Entity Framework 中的多个动态排序依据

Question

Dim receipts As IQueryable(Of ReceiptEntity) = db.Receipts

'code to filter removed for brevity

Dim sorts() As String = SortExpression.Split(";")

For Each sort As String In sorts
    Dim sortParts() As String = sort.Split(" ")
    If sortParts(1).ToLower = "true" Then
        receipts = receipts.OrderBy(Of ReceiptEntity)(sortParts(0).ToString(), SortDirection.Ascending)
    Else
        receipts = receipts.OrderBy(Of ReceiptEntity)(sortParts(0).ToString(), SortDirection.Descending)
    End If
Next

SortExpression 像“field1 true;field2 false;field3 true”一样出现

我想要发生的是查询具有多个 order by 字段，正在发生的事情是只应用最后一个 order by。我在这里做错了什么？

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这是工作结果的样子：

Dim receipts As IOrderedQueryable(Of ReceiptEntity) = db.Receipts.Include(Function(r) r.LineItems).Include(Function(r) r.Payments)

Dim sorts() As String = SortExpression.Split(";")
Dim sortParts() As String
sortParts = sorts(0).Split(" ")
If sortParts(1).ToLower = "true" Then
    receipts = receipts.OrderBy(sortParts(0).ToString())
Else
    receipts = receipts.OrderByDescending(sortParts(0).ToString())
End If


For Each sort As String In sorts.Skip(1)
    sortParts = sort.Split(" ")
    If sortParts(1).ToLower = "true" Then
        receipts = receipts.ThenBy(sortParts(0).ToString())
    Else
        receipts = receipts.ThenByDescending(sortParts(0).ToString())
    End If
Next

Answer 1

您必须使用ThenBy而不是OrderBy用于第二次和所有后续排序操作。