Ms access Access VBA：在窗体上迭代控件，仅显示某些控件类型具有的属性

我试图遍历表单上的控件，以显示支持ControlSource的控件的ControlSource属性

我发现识别具有ControlSource属性的控件相对容易。问题在于访问这些控件的属性。泛型控件对象没有ControlSource属性。如果我使用的是另一种语言，我只需将一个listbox控件强制转换为listbox对象，例如，以访问ControlSource属性。但我的理解是，在VBA中没有类型继承，所以我不能将一种类型的对象强制转换为另一种类型

那么，如何访问支持该属性的控件的ControlSource属性呢

以下是我目前的代码：

Private Sub IterateControlsOnForm()
Dim frm As Form, formName As String
' The only controls that have a ControlSource property are either
'   BoundObjectFrame controls or ListBox controls.
Dim ctrl As Control
Dim boundObjectFrame As boundObjectFrame, listBoxCtrl As listBox
Dim boundObjectFrameTypes() As String, listBoxTypes() As String
Dim ctrlType As String

    formName = "MAINFORM"

    ' Useful way of populating a string array - use Split function.
    '   Array function only works with Variants.
    boundObjectFrameTypes = _
        Split("CheckBox,ComboBox,CustomControl,GroupLevel", ",")
    listBoxTypes = Split("OptionButton,OptionGroup,TextBox,TextBox", ",")

    ' Assumes form is open.
    Set frm = Forms(formName)
    For Each ctrl In frm.Controls
        ' Ignore controls that do not have a ControlSource property.
        ctrlType = TypeName(ctrl)
        If IsStringInArray(ctrlType, boundObjectFrameTypes) Then
            ' **** FOLLOWING LINE FAILS ****
            Set boundObjectFrame = ctrl
            Debug.Print boundObjectFrame.Name & "(" & ctrlType & ") " & _
                "ControlSource Property: " & boundObjectFrame.ControlSource
        ElseIf IsStringInArray(ctrlType, listBoxTypes) Then
            ' **** FOLLOWING LINE FAILS ****
            Set listBoxCtrl = frm.Controls(ctrl.Name)
            Debug.Print listBoxCtrl.Name & "(" & ctrlType & ") " & _
                "ControlSource Property: " & listBoxCtrl.ControlSource
        End If
    Next ctrl
End Sub

---

我尝试了两种方法将通用控件对象转换为具有ControlSource属性的更特定控件。请参阅两条注释“**以下行失败**”

使用对象如何

Private Sub IterateControlsOnForm()
Dim frm As Form, formName As String
' The only controls that have a ControlSource property are either
'   BoundObjectFrame controls or ListBox controls.
Dim ctrl As Control
Dim boundObjectFrame As Object, listBoxCtrl As Object
Dim boundObjectFrameTypes As String, listBoxTypes As String
Dim ctrlType As String

    formName = "MAINFORM"

    ' Useful way of populating a string array - use Split function.
    '   Array function only works with Variants.
    boundObjectFrameTypes = _
        ",CheckBox,ComboBox,CustomControl,GroupLevel"
    listBoxTypes = ",OptionButton,OptionGroup,TextBox,TextBox"

    ' Assumes form is open.
    Set frm = Forms(formName)
    For Each ctrl In frm.Controls
        ' Ignore controls that do not have a ControlSource property.
        ctrlType = TypeName(ctrl)
        If InStr(boundObjectFrameTypes, "," & ctrlType) Then
            Set boundObjectFrame = ctrl
            Debug.Print boundObjectFrame.Name & "(" & ctrlType & ") " & _
                "ControlSource Property: " & boundObjectFrame.ControlSource
        ElseIf InStr(listBoxTypes, "," & ctrlType) Then
            Set listBoxCtrl = frm.Controls(ctrl.Name)
            Debug.Print listBoxCtrl.Name & "(" & ctrlType & ") " & _
                "ControlSource Property: " & listBoxCtrl.ControlSource
        End If
    Next ctrl
End Sub

有了VBA，您还可以在下一步使用On Error Resume，尽管我同意通常最好避免错误

formName = "MAINFORM"

Set frm = Forms(formName)
For Each ctrl In frm.Controls
On Error Resume Next
    Debug.Print ctrl.Name _
        & " ControlSource Property: " & ctrl.ControlSource
    If Err.Number = 438 Then
        Err.Clear
    End If
Next

---

好极了，工作得很好！我从未想过使用对象数据类型，因为我假设它没有ControlSource属性。对于遇到这个问题的其他人，我还发现了另一个解决方法：ctrl.Properties（“ControlSource”）也起作用，其中ctrl是一个控制对象，正如上面的代码所示。对象具有分配给它的任何属性。