Top of my head: If a control had nested controls then use recursion to drill down ( check the ctrl.Count property)

>But for me this does not seem to work, as I put my "maskit" controls in panels and pageframes and other containers. Yes, I have to write a Maskit routine (for each of those containers) that contains a "for each ctrl in me.controls". There's probably a way to handle this a the form level too of course.
>
>Kind regards,
>
>Marc
>
>
>
>>Hi,
>>TBH, I'm rusty on DataTable/DataView stuff but it looks as if you and Bonnie have sorted it. It did occur to me that if the MasKit method was the only item in the interface you could keep the txtBase class lighter by handling this is the form method:

 Friend Sub MasKit(ByVal cols As DataColumnCollection)
>>        For Each Ctrl In Me.Controls
>>            If (TypeOf Ctrl Is IControlMaskit) Then
>>                Dim icm As IControlMaskit = CType(Ctrl, IControlMaskit)
>>                 If icm.Mask <> "" Then
>>                    Exit Sub
>>                End If
>>
>>                Dim B As Binding = Ctrl.DataBindings.Item(0)
>>
>>                Dim O As Object = B.DataSource
>>                If Not (TypeOf O Is DataTable) Then
>>                    O = CType(O, DataView).Table
>>                End If
>>
>>                Dim c As DataColumn = CType(O, DataTable).Columns(B.BindingMemberInfo.BindingField)
>>                Select Case c.DataType
>>                    Case GetType(System.String)
>>                        ' Possible error c.MaxLength can be negative.....
>>                        icm.Mask = ">" & New String("A", c.MaxLength)
>>                    Case GetType(System.DateTime)
>>                        icm.Mask = ">##/AAA/##"
>>                End Select
>>            End If
>>        Next
>>    End Sub
>>End Class
>>
>>Public Interface IControlMaskit
>>    Property Mask() As String
>>End Interface

This would also allow you to use this with controls other than just TextBox...
>>
>>>It's shorter, it's more elegant, and it works.
>>>
>>>Thanks a lot.
>>>
>>>Marc
>>>
>>>PS : it does not solve my conundrum that B.Datasource turns out to be a BindingSource that steadfastly refuses to divulge to which table the field belongs to which the control is bound.
>>>
>>>
>>>>Will this do what you need:

Friend Sub MasKit(ByVal cols As DataColumnCollection)
>>>>        For Each Ctrl In Me.Controls
>>>>            If (TypeOf Ctrl Is IControlMaskit) Then
>>>>                CType(Ctrl, IControlMaskit).MaskIt(cols)
>>>>            End If
>>>>        Next
>>>>    End Sub

   Friend Sub MaskIt(ByVal cols As DataColumnCollection) Implements IControlMaskit.MaskIt
>>>>        If Me.Mask <> "" Then
>>>>            Exit Sub
>>>>        End If
>>>>
>>>>        Dim B As Binding = Me.DataBindings.Item(0)
>>>>
>>>>        Dim O As Object = B.DataSource
>>>>        If Not (TypeOf O Is DataTable) Then
>>>>            O = CType(O, DataView).Table
>>>>        End If
>>>>
>>>>        Dim c As DataColumn = CType(O, DataTable).Columns(B.BindingMemberInfo.BindingField)
>>>>
>>>>        Select Case c.DataType
>>>>            Case GetType(System.String)
>>>>                ' Possible error since MaxLength can be negative.....
>>>>                Me.Mask = ">" & New String("A", c.MaxLength)
>>>>            Case GetType(System.DateTime)
>>>>                Me.Mask = ">##/AAA/##"
>>>>        End Select
>>>>    End Sub

If not then at least it's a bit shorter (s)
>>>>