VB.NET LINQ 组加入问题

Question

好吧，我知道有很多关于这个问题的帖子，但我花了几个小时试图解决这个问题，但我的大脑完全失去了知觉。

这是

我有一个包含 3 个属性（数量、服务、名称）的对象列表，

我希望列表中包含所有名称和服务（有点交叉连接）以及相应行的分组数量。不清楚，我猜

数量 服务名称
3 Srv2 鲍勃
4 Srv2 保罗
2 Srv1 保罗
1 Srv2 Nick

我想要作为输出
所有服务以及所有名称和相应数量（如果没有则为 0）

Srv1 Paul 2
Srv1 鲍勃 0
Srv1 尼克 0
Srv2 保罗 4
Srv2 鲍勃 3
Srv2 Nick 1

这是我到目前为止得到的结果，但我什至没有得到预期的结果 我非常确定有一种非常简单的方法可以实现我想要的...我会欢迎一些帮助...

谢谢

    Dim services = (From a In interventions Select New With {.Service = a.Service}).Distinct()
    Dim months = (From b In interventions Select New With {.Month = b.DateHeureIntervention.Month}).Distinct()

    'Dim query = (From s In services _
    '             From m In months _
    '             From i In interventions.Where(Function(x) x.Service = s.Service And x.DateHeureIntervention.Month = m.Month).DefaultIfEmpty(New Intervention()) _
    '             Select New ChartItem With {.Service = s.Service, _
    '                                        .Name = MonthName(m.Month), _
    '                                        .Quantite = i.Quantite}).ToList()

    'Return (From q In query _
    '       Group By srv = q.Service, n = q.Name Into Group _
    '       Select New ChartItem With {.Name = n, _
    '                                  .Service = srv, _
    '                                  .Quantite = Group.Sum(Function(i) i.Quantite)}).ToList()


    Dim q = (From i In interventions _
            Group Join s In services On s.Service Equals i.Service Into si = _
            Group Join m In months On m.Month Equals i.DateHeureIntervention.Month _
            From x In si.DefaultIfEmpty() _
            Group By m = i.DateHeureIntervention.Month, srv = i.Service Into Group _
            Select New ChartItem With {.Service = srv, _
                                       .Name = MonthName(m), _
                                       .Quantite = Group.Sum(Function(y) y.i.Quantite)}).ToList()

    Return q

Answer 1

我得到的是我的结果，肯定有更好的方法，但无论如何，它有效

    Dim months As List(Of Integer) = (From b In interventions Select b.DateHeureIntervention.Month).Distinct().ToList()
    Dim services As List(Of String) = (From c In interventions Select c.Service).Distinct().ToList()

    Dim q = (From s In services _
             From m In months _
             Select New ChartItem With {.Name = MonthName(m), _
                                        .Service = s, _
                                        .Quantite = (From i In AccesDonneesHelper.GetInterventionsDetails() _
                                                     Where i.Service = s And i.DateHeureIntervention.Month = m _
                                                     Select i.Quantite).Sum()}).ToList()