LINQ对实体不识别方法-简单的删除语句

Question

我有一个GridView和一行被删除，我触发GridView1_RowDeleting子，但我收到一个错误"LINQ到实体不识别方法'System.Web.UI.WebControls.TableCell get_Item(Int32)'方法，这个方法不能被翻译成存储表达式。"代码:

Private Sub GridView1_RowDeleting(sender As Object, e As System.Web.UI.WebControls.GridViewDeleteEventArgs) Handles GridView1.RowDeleting
    ' The deletion of the individual row is automatically handled by the GridView.
    Dim dbDelete As New pbu_housingEntities
    ' Remove individual from the bed.
    Dim remove_bed = From p In dbDelete.Beds _
                     Where p.occupant = GridView1.Rows(e.RowIndex).Cells(3).Text _
                     Where p.room = GridView1.Rows(e.RowIndex).Cells(6).Text _
                     Where p.building = GridView1.Rows(e.RowIndex).Cells(5).Text _
                     Order By p.id Descending _
                     Select p
    remove_bed.First.occupant = ""
    dbDelete.SaveChanges()
    ' Increase number of open spaces in room.
    Dim update_occupancy = From p In dbDelete.Rooms _
                           Where p.room1 = GridView1.Rows(e.RowIndex).Cells(6).Text
                           Where p.building = GridView1.Rows(e.RowIndex).Cells(5).Text _
                           Select p
    update_occupancy.First.current_occupancy = update_occupancy.First.current_occupancy - 1
    dbDelete.SaveChanges()
End Sub

出错的具体行是:

remove_bed.First.occupant = ""

Answer 1

这是因为Linq查询被转换为SQL，而没有办法将GridView1.Rows(e.RowIndex).Cells(3).Text转换为SQL。您需要从GridView中提取值，然后在查询

中使用它们

Dim occupant As String = GridView1.Rows(e.RowIndex).Cells(3).Text
Dim room As String = GridView1.Rows(e.RowIndex).Cells(6).Text
Dim building As String = GridView1.Rows(e.RowIndex).Cells(5).Text
Dim remove_bed = From p In dbDelete.Beds _
                 Where p.occupant = occupant _
                 Where p.room = room _
                 Where p.building = building _
                 Order By p.id Descending _
                 Select p

Answer 2

您必须在执行查询之前将这些值放入变量中，否则实体提供程序将尝试将整个对象拉入查询并在试图将其转换为SQL语句时访问其属性-这将失败，因为没有等同的SQL。