Question

我是这样从数据库中获取数据的。

 Dim query = From t1 In TBL1 _
             Join t2 In TBL2 On t1.ID Equals t2.ID _
             Join t3 In TBL3 On t1.ID Equals t3.ID _
             Group Join t4 In t1 _
                   On t1.ID Equals t4.ID _
                   Into t4_Grp = Group _
             Select t1, t2, t3, t4_Grp

当用户执行搜索时，我可以像这样过滤查询结果。
```
query = query.Where(Function(o) o.t1.ID = lngID)
```
一切都很好，直到我想要对t4_Grp进行lambda处理。我不知道如何对t4_Grp使用lambda表达式？

Answer 1

过去我用过这个来进行一些强制分组。

private void ProducePivotAnalytic <T, K>(IEnumerable<T> colletion, Func<T, K> pivot)
{
    var grouped =
        from n in colletion
            group n by pivot(n) into g
            select new { theKey = g.Key, theValue = g };
    // do some stuff with your grouped collection.
}


ProducePivotAnalytic<List<DateTime>, DayOfWeek>(
        myDates,
            (x) => (x.DayOfWeek) );

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