VB.NET & Linq：在另一列中汇总数据表列和按日期分组
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VB.NET & Linq: Sum datatable column and Group by date in another column
提问by ruedi
I have a typedDataset (ds) and its datatable(dt). The datatable has the columns Date(ttmmyyy) and Worktime. I want to sum the Worktime by month. I already accomplished to sum the Worktime with
我有一个 typedDataset (ds) 和它的数据表 (dt)。数据表具有列Date(ttmmyyy) 和Worktime. 我想按月总结工作时间。我已经完成了总结工作时间
Dim sum = dt.AsEnumerable().Sum((Function(x) x.Worktime))
I need help with group this by month.
我需要帮助按月分组。
回答by Carlos Landeras
I created a table with your fields and the following query worked nice:
我用您的字段创建了一个表，以下查询效果很好：
Dim query = From row In dt
Group row By VarDate= row.Field(Of DateTime)("Date") Into MonthGroup = Group
Select New With {
Key VarDate,
.Worktime = MonthGroup.Sum(Function(r) r.Field(Of Int32)("Worktime"))
}
Used variable VarDatebecause Date is reserved for it's own class.
使用变量，VarDate因为 Date 是为它自己的类保留的。
Output:
输出：
Vardate: 10/15/2013 Worktime: 150
Vardate: 10/16/2013 Worktime: 180
投票日：10/15/2013 工作时间：150
投票日：10/16/2013 工作时间：180
EDIT:
编辑：
To get the output just use:
要获得输出，只需使用：
For Each obj In query
Dim datet = obj.VarDate
Dim WorkH = obj.Worktime
Next
To avoid declarying types when using linq, insert the line: option infer onon the very first line of the vb.net document ( so you can use dim datet = obj.Vardate ) without declaring the type. It is like var in c#
为避免在使用 linq 时声明类型option infer on，请在 vb.net 文档的第一行插入行：（因此您可以使用 dim datet = obj.Vardate ）而不声明类型。它就像 c# 中的 var
