Vb.net 从linq查询返回数据表

我试图从linq查询返回数据表，但收到错误消息。我正在VS2012中使用.net framework 4.0

<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------”

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

无法将类型为“d”的对象强制转换为类型为“System.Collections.Generic.IEnumerable`1[System.Data.DataRow]”的对象。

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我在这里试过这个例子，但运气不好。在VS2012中，我没有获得CopyToDataTable。

我已经尝试过这个方法，而且效果很好

<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

    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

    For Each item In query
        Dim dr As DataRow = dt.NewRow()
        dr("OfficeID") = item.OfficeID
        dr("OfficeName") = item.OfficeName
        dt.Rows.Add(dr)
    Next

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另一种方法是使用

Aggregate

扩展方法

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为什么它必须是DataTable？StatfficeAccess表没有office name实体。我需要返回办公室ID和办公室名称。可以是数据集，因为我需要用下拉列表控件绑定结果。