子類/超類 - 如果一個子類被轉換爲其超類，是否有一種方法可以使用子類的重載屬性？

Question

對不起，如果標題不是很清楚。這是一個VB.NET（2010）問題

我有一個叫做「設備」的超類，它有許多繼承它的子類。其中一些子類也有子類。特別是，我有一個名爲「TwinCatIntegerDevice」的類，它繼承了繼承「Device」的「TwinCatDevice」。

設備看起來像這樣的相關部分：

Public Class Device 

Private _Setpoints As New List(Of Double) 
Public Overridable Property Setpoints As List(Of Double) 
    Get 
     Return _Setpoints 
    End Get 
    Set(ByVal value As List(Of Double)) 
     _Setpoints = value 
     _SetpointsTb.Clear() 
     For Each setpoint In value 
      Dim setpointTb As New TextBox 
      setpointTb.Text = setpoint.ToString 
      _SetpointsTb.Add(setpointTb) 
     Next 
    End Set 
End Property 
Private _SetpointsTb As New List(Of TextBox) 
    Public Overridable Property SetpointsTb As List(Of TextBox) 
     Get 
      Return _SetpointsTb 
     End Get 
     Set(ByVal value As List(Of TextBox)) 
      _SetpointsTb = value 
      Me._Setpoints.Clear() 
      For Each setpoint In value 
       Me._Setpoints.Add(setpoint.Text) 
      Next 
     End Set 
    End Property 

End Class 

的TwinCatDevice類不超載設定值或SetpointsTb。 的TwinCatIntegerDevice類做：

Public Class TwinCatIntegerDevice 
    Inherits TwinCatDevice 

    Private _Setpoints As New List(Of Integer) 
    Public Overloads Property Setpoints As List(Of Integer) 
     Get 
      Return _Setpoints 
     End Get 
     Set(ByVal value As List(Of Integer)) 
      _Setpoints = value 
      _SetpointsTb.Clear() 
      For Each setpoint In value 
       Dim setpointTb As New TextBox 
       setpointTb.Text = setpoint.ToString 
       _SetpointsTb.Add(setpointTb) 
      Next 
     End Set 
    End Property 
    Private _SetpointsTb As New List(Of TextBox) 
    Public Overloads Property SetpointsTb As List(Of TextBox) 
     Get 
      Return _SetpointsTb 
     End Get 
     Set(ByVal value As List(Of TextBox)) 
      _SetpointsTb = value 
      Me._Setpoints.Clear() 
      For Each setpoint In value 
       Me._Setpoints.Add(setpoint.Text) 
      Next 
     End Set 
    End Property 

End Class 

現在的問題。我嘗試使用像這樣的子程序設置設定值：

Private Sub FetchDeviceRecipe(ByRef device As Device, ByRef excelSheet As ExcelWorksheet, ByVal row As Integer) 
     Dim lastCol As Integer = NumberOfProcessSteps + 1 
     Try 
      For col = 2 To lastCol 
       Dim setpoint As New TextBox 
       setpoint.Text = excelSheet.Cells(row, col).Value 
       device.SetpointsTb.Add(setpoint) 
      Next 
      device.SetpointsTb = device.SetpointsTb 
     Catch ex As Exception 
      MsgBox(ex.Message) 
     End Try 
    End Sub 

（我知道這是可怕的代碼：X，我是一個初學者）

重要的是，我傳遞的設備作爲設備超類（這樣我就不必爲每個子類型有一個單獨的子例程）。

當我做了一個名爲「ThisDevice」已經傳遞給子程序後TwinCatIntegerDevice：

MsgBox("As Device: " & CType(ThisDevice, Device).Setpoints.Count.ToString & vbNewLine & _ 
        "As TwinCatDevice: " & CType(ThisDevice, TwinCatDevice).Setpoints.Count.ToString & vbNewLine & _ 
        "As TwinCatIntegerDevice: " & CType(ThisDevice, TwinCatIntegerDevice).Setpoints.Count.ToString) 

我得到以下（9在這種情況下設定值的正確的號碼）：

As Device: 9 
As TwinCatDevice: 9 
As TwinCatIntegerDevice: 0 

有沒有人知道爲什麼TwinCatInteger設備類顯然有一個不同的設定點變量，當它被轉換爲它的超類設備？

對不起，如果這看起來有點不一致。任何幫助將是偉大的！即使在形式或其他方面。我仍然試圖把這整個VB.NET的事情弄清楚。

Answer 1

我認爲你想要做的是在「TwinCatIntegerDevice」類中刪除你的「OverLoads」關鍵字，並用關鍵字「Shadows」替換它。