c＃使用linq按数据表中的多个列进行分组

我在数据表中有三列：字符串，日期时间和小数。 我想按字符串和十进制列分组，对于分组的行，我想要对小数值求和。 我知道如何进行求和部分，但是如何在数据表中对两个不同的列进行分组？

到目前为止，这是我的代码无法正常工作：

var newSort = from row in objectTable.AsEnumerable() group row by new {ID = row.Field("resource_name"), time1 = row.Field("day_date")} into grp orderby grp.Key select new { resource_name1 = grp.Key.ID, day_date1 = grp.Key.time1, Sum = grp.Sum(r => r.Field("actual_hrs")) }; 

Answer 1

我不认为你给了我们完整的故事。 除了不使用匿名类型的命令（您提供的代码不会编译），您的查询应该按照您想要的方式工作。 我把它放在LINQPad中：

 var objectTable = new DataTable(); objectTable.Columns.Add("resource_name",typeof(string)); objectTable.Columns.Add("day_date",typeof(DateTime)); objectTable.Columns.Add("actual_hrs",typeof(decimal)); objectTable.Rows.Add(1, DateTime.Today, 1); objectTable.Rows.Add(2, DateTime.Today, 2); var newSort = from row in objectTable.AsEnumerable() group row by new {ID = row.Field("resource_name"), time1 = row.Field("day_date")} into grp select new { resource_name1 = grp.Key.ID, day_date1 = grp.Key.time1, Sum = grp.Sum(r => r.Field("actual_hrs")) }; newSort.Dump(); 

……我得到了这些结果：

 resource_name1 | day_date1 | Sum 1 | 7/1/2011 12:00:00 AM | 1 2 | 7/1/2011 12:00:00 AM | 2 

Answer 2

使用此代码

 var newSort = from row in objectTable.AsEnumerable() group row by new {ID = row.Field("resource_name"), time1 = row.Field("day_date")} into grp orderby grp.Key select new { resource_name1 = grp.Key.ID, day_date1 = grp.Key.time1, Sum = grp.Sum(r => Convert.ToDecimal(r.ItemArray[2])) }; 

Answer 3

对于那些想要在Vb.net中使用解决方案的人来说，这是一个例子：

 Dim workTable As DataTable = New DataTable("Customers") Dim workCol As DataColumn = workTable.Columns.Add("ID", Type.GetType("System.Int32")) workTable.Columns.Add("Total", Type.GetType("System.Decimal")) workTable.Columns.Add("Compra", Type.GetType("System.Decimal")) Dim row As DataRow = workTable.NewRow() row("id") = 2 row("total") = 1.5 row("compra") = 3 workTable.Rows.Add(row) row = workTable.NewRow() row("id") = 1 row("total") = 1.5 row("compra") = 3.3999999999999999 workTable.Rows.Add(row) row = workTable.NewRow() row("id") = 1 row("total") = 1.5 row("compra") = 5 workTable.Rows.Add(row) Dim detalles As IEnumerable(Of DataRow) = workTable.AsEnumerable() Dim query = From detalle In detalles.AsEnumerable() _ Group detalle By grupoClave = New With _ { _ Key .C2 = detalle("id"), _ Key .C4 = detalle("total")} Into g = Group _ Select New With _ { _ .Col2 = g(0).Field(Of Integer)("id"), _ .Col3 = g(0).Field(Of Decimal)("total"), _ .Col4 = g.Sum(Function(fact) fact.Field(Of Decimal)("compra")) _ } For Each p In query Console.WriteLine((p.Col2 & p.Col3 & p.Col4)) Next