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Question

我不断收到试图执行这些代码时这个错误，甚至放置CTYPE围绕价值和其定义为双后键入“双是不是有效？

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 occupant As String = GridView1.Rows(e.RowIndex).Cells(2).Text 
    Dim room As String = GridView1.Rows(e.RowIndex).Cells(5).Text 
    Dim building As String = GridView1.Rows(e.RowIndex).Cells(4).Text 
    Dim find_id = From p In dbDelete.Residents _ 
        Where p.person_name = occupant _ 
        Select p 


    Dim remove_bed = From p In dbDelete.Beds _ 
        Where p.occupant = find_id.FirstOrDefault.id _ 
        Where p.room = room _ 
        Where p.building = building _ 
        Order By p.id Descending _ 
        Select p 
    remove_bed.First.occupant = CType(0, Double) 
    dbDelete.SaveChanges() 

    ' Increase number of open spaces in room. 
    Dim update_occupancy = From p In dbDelete.Rooms _ 
          Where p.room1 = room 
          Where p.building = building _ 
          Select p 

    update_occupancy.First.current_occupancy = update_occupancy.First.current_occupancy - 1 
    dbDelete.SaveChanges() 

End Sub 

Answer 1

我怀疑问题出在这行：

Where p.occupant = find_id.FirstOrDefault.id _ 

是这两个同类型的？我怀疑这条线的原因是因为在之前的另一个表中，您使用的是occupant作为此人的名字。我会检查where子句中的其他值是否与您正在比较它们的类型相匹配。

，它可能出现的错误是在分配行的原因是，直到你在它上面运行First未进行查询。错误很可能在查询中，而不是在分配中。

Answer 2

它不能将空字符串转换为双精度字符串。放在一个if语句检查一个空字符串，如果是空的，则设置双0