Question

我正在尝试从linq查询返回数据表但收到错误消息。我在VS2012中使用.net framework 4.0。

directions.src = "ball.gif";

'----------------------------'

<Table>
Public Class StaffOfficeAccess

<Column(CanBeNull:=False, IsPrimaryKey:=True, IsDbGenerated:=True)>
Public Property StaffOfficeAccessID As Int32 = 0
<Column>
Public Property StaffID As Int32 = 0
<Column>
Public Property OfficeID As Int32 = 0
<Column(IsVersion:=True, IsDbGenerated:=True)>
Public Property Version As Byte()
End Class

'-------错误----------'

无法将类型为'd__61 Public Function GetByStaffID(ByVal staffID As Int32) As DataTable Dim query As IEnumerable(Of DataRow) = CType((From oa In db.StaffOfficeAccess.AsEnumerable() _ Join o In db.Office.AsEnumerable() On oa.OfficeID Equals o.OfficeID _ Select oa.OfficeID, o.OfficeName), Global.System.Collections.Generic.IEnumerable(Of Global.System.Data.DataRow)) Dim table As DataTable = System.Data.DataTableExtensions.CopyToDataTable(query) Return table End Function 2 [System.Int32，System.String]]'的对象强制转换为'System.Collections.Generic.IEnumerable`1 [System.Data.DataRow] ”。

我在这里尝试过这个例子https://msdn.microsoft.com/en-us/library/bb396189%28v=vs.110%29.aspx但没有运气。我在VS2012中没有得到CopyToDataTable。

Answer 1

使用Aggregate扩展方法MSDN

的另一种方法

Dim dt As New DataTable()
dt.Columns.Add("OfficeID", GetType(Integer))
dt.Columns.Add("OfficeName", GetType(String))

Dim query = From oa In db.StaffOfficeAccess.AsEnumerable()
            Join o In db.Office.AsEnumerable() 
            On oa.OfficeID Equals o.OfficeID
            Select oa.OfficeID, o.OfficeName

query.Aggregate(Of DataTable)(dt, 
                              Function(dtb, o)
                                  Dim dr As DataRow = dtb.NewRow()
                                  dr.SetField("OfficeID", o.OfficeID)
                                  dr.SetField("OfficeName", o.OfficeName)
                                  dtb.Rows.Add(dr)
                                  Return dtb
                              End Function)

从linq查询返回数据表

1 个答案: