我正在寻找将GroupBy添加到Linq表动态中的核心语法,因为组参数可以在用户界面中更改。
基本上我有一个林克。EntitySet,我想为可变参数添加GroupBy
天,周月年度
而不是像那样写4个查询
data.View.GroupBy(Function(x) x.Moment.Date).OrderBy(Function(x) x.Key).Select(Function(x) New With {.Date = x.Key, .Count = x.Count()})
data.View.GroupBy(Function(x) x.Moment.Week).OrderBy(Function(x) x.Key).Select(Function(x) New With {.Date = x.Key, .Count = x.Count()})
data.View.GroupBy(Function(x) x.Moment.Month).OrderBy(Function(x) x.Key).Select(Function(x) New With {.Date = x.Key, .Count = x.Count()})
data.View.GroupBy(Function(x) x.Moment.Year).OrderBy(Function(x) x.Key).Select(Function(x) New With {.Date = x.Key, .Count = x.Count()})
我喜欢通过表达式树动态添加组,或者有更简单的方法吗?
谢谢你的建议!
令人惊讶的是,它比我想象的要简单!
Private Function bar(x As Date) As Object
Select Case ddlStatRange.SelectedValue
Case 1
Return x.Month
Case 2
Return x.Month
Case 3
Return x.Year
Case Else
Return x.Date
End Select
End Function
Dim foo = data.View.GroupBy(Function(x) bar(x.Moment)).OrderBy(Function(x) x.Key).Select(Function(x) New With {.Date = x.Key, .Count = x.Count()})
无论如何,如果有人有更好的想法:D