以下是我的LINQ查询:
Dim JoinedResult = From t1 In temp.AsEnumerable() _
Group Join t2 In tbCity.AsEnumerable() _
On t1.Field(Of String)("City") Equals t2.Field(Of String)("city_name") _
Into RightTableResults = Group _
From t In RightTableResults.DefaultIfEmpty
Select New With
{
.ID = t1.Item("ID"),
.CID = If(t Is Nothing,
1,
t.Item("city_gid"))
}
如何将值从“JoinedResult”复制到数据表?
注意:
JoinedResult.CopyToDataTable()
答案 0 :(得分:3)
CopyToDataTable
已经存在。但问题是你想从匿名类型创建一个DataTable
“从头开始”。这不起作用。
CopyToDataTable
仅是IEnumerable<DataRow>
的扩展名。因此,您必须从加入的DataRow
中选择一个 DataTables
:
Dim query = From t1 In temp.AsEnumerable() _
Group Join t2 In tbCity.AsEnumerable() _
On t1.Field(Of String)("City") Equals t2.Field(Of String)("city_name") Into RightTableResults = Group
From t In RightTableResults.DefaultIfEmpty
Select t1
Dim table = query.CopyToDataTable()
或使用使用反射的this ObjectShredder
,因此不是最有效的方式(C# implementation)。
除此之外,你为什么还需要DataTable
?您还可以将匿名类型用作DataSource,或者创建一个可以从查询结果初始化的自定义类。
修改:您还可以创建包含所需列的自定义DataTable
,例如(来自您的评论):
Dim tbTemp As New DataTable
tbTemp.Columns.Add("ID")
tbTemp.Columns.Add("CID")
Dim query = From t1 In temp.AsEnumerable()
Group Join t2 In tbCity.AsEnumerable() On
t1.Field(Of String)("City") Equals t2.Field(Of String)("city_name")
Into RightTableResults = Group
From t In RightTableResults.DefaultIfEmpty
Select New With {.ID = t1.Item("ID"), .City_Gid = t.Item("city_gid")}
For Each x In query
tbTemp.Rows.Add(x.ID, x.City_Gid)
Next