VB.NET GroupBy LINQ语句

你不需要使用分组方式。

Public ReadOnly Property AllOrders() As List(Of Order)
Get
     Return Items.Select(Function(i) i.OrderID).Distinct.Select(Function(p) New Order(p)).ToList()
End Get
End Property

如果要按order上的OrderedDate排序,只需在ToList之前添加orderby子句

Public ReadOnly Property AllOrders() As List(Of Order)
Get
     Return Items.Select(Function(i) i.OrderID).Distinct _
                 .Select(Function(p) New Order(p)) _
                 .OrderBy(Function(s) s.DateOrdered).ToList()
End Get
End Property

通过将OrderBy放在GroupBy之后,可以指示它对组进行排序。一组订单没有一个日期。我在想你可能想做的是切换OrderBy和GroupBy;除非GroupBy丢失任何先前的排序顺序,否则您必须对每个组进行排序。

这在我看来也是不对的

.GroupBy(Function(o As Order) New Order(o.OrderID))

.GroupBy(Function(o As Order) o.OrderID)

我说了F,然后用了一些不太漂亮的代码:

Public ReadOnly Property AllOrders() As List(Of Order)
    Get
        Dim ids = Items.Select(Function(i As OrderItem) i.OrderID).Distinct()
        Dim orders As New List(Of Order)
        For Each i As Integer In ids
            orders.Add(New Order(i))
        Next
        Return orders.OrderBy(Function(o As Order) o.DateOrdered).ToList
    End Get
End Property

如果有人有林奇尔的方法,我宁愿这样做。否则,我想这一堆乱七八糟的东西就只能这样了。