Question

我有以下数据表：

DefectTypeId   EntityId      DefectId     Remark
------------------------------------------------
1              29000         100          Defect
2              29000         100          Defect
3              29000         200          Ok
1              30000         100          Defect
2              30000         150          
9              31000         100          Defect
10             31000         100          Defect 
12             31000         200          Ok

如何使用linq获取此表或列表？

EntityId   Remark
------------------------
29000      Defect, Ok
30000      Defect
31000      Defect, Ok

提前致谢

修改

我试过了，但它没有用（行没有分组）：

Dim query = dt.Select("Remark IS NOT NULL").AsEnumerable().GroupBy(
            Function(r) New With {
                .EntityId = r.Field(Of Integer)("EntityId"),
                .DefectId = r.Field(Of Integer)("DefectId"),
                .Remark = r.Field(Of String)("Remark")
            }).[Select](
            Function(g) New With {
                g.Key.EntityId,
                .Remark = String.Join(",", g.Select(Function(i) i("Remark")))
            })

然后我尝试了这个：

Dim query = (From row In dt.Select("Remark IS NOT NULL")
             Group By EntityId = row.Field(Of Integer)("EntityId"),
                 DefectId = row.Field(Of Integer)("DefectId"),
                 Remark = row.Field(Of String)("Remark") Into g = Group) _
            .Select(Function(i) New With {
                i.EntityId,
                .Remark = String.Join(",", i.Remark)
            })

它更好，但它还不是预期的结果。结果如下：

EntityId   Remark
------------------------
29000      Defect
29000      Ok
30000      Defect
31000      Defect
31000      Ok

我可以使用foreach获得我想要的东西，但想知道是否有可能在单个Linq指令中获得目标（每个实体一行）。谢谢。

Answer 1

从您的答案开始并向后工作，您希望按EntityId分组并加入不同的Remark。使用现有的lambda查询作为基础，只需简化它（虽然我会做＆＃34;备注IS NOT NULL＆＃34;通常在LINQ中）：

Dim Ans = dt.Select("Remark IS NOT NULL") _
            .GroupBy(Function(r) r.Field(Of Integer)("EntityId"), Function(r) r.Field(Of String)("Remark")) _
            .Select(Function(rg) New With {
                .EntityId = rg.Key,
                .Remark = String.Join(", ", rg.Distinct())
            })

使用VB Query Comprehension的一些优点，你也可以这样做：

Dim Ans2 = From r In dt.Select("Remark IS NOT NULL")
           Group r.Field(Of String)("Remark") By Key = r.Field(Of Integer)("EntityId") Into Group
           Select New With {.EntityId = Key, .Remark = String.Join(", ", Group.Distinct())}

GroupBy with linq to DataTable

1 个答案: