I was going to suggest to Marc some of what you just posted, Viv ... but, since it's VB and I didn't quite know how to translate what my C# suggestion would be: if (Ctrl is IControlMaskit), I figured I'd leave it alone, since it worked. Hmmm, well, checking my favorite online C#-to-VB converter, I see that it would have translated that just fine ... well, there goes my excuse for being a slacker! <g>

~~Bonnie


>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)
>
>>

>>    Private Sub frmXXX_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
>>        Me.MasKit(Me.XXXDataset.XXX.Columns)
>>    End Sub
>>

>>
>>so, cols is really Me.XXXDataset.XXX.Columns is a DataColumnCollection, belonging to a datatable ... I think.
>>
>>in my baseform I have :
>>

>>    Friend Sub MasKit(ByVal cols As DataColumnCollection)
>>        Dim ctrl2 As IControlMaskit = Nothing
>>        For Each Ctrl As Control In Me.Controls
>>            Dim lApplicable As Boolean = True
>>            Try
>>                ctrl2 = Ctrl
>>            Catch 
>>                lApplicable = False
>>            End Try
>>            If lApplicable Then
>>                ctrl2.MaskIt(cols)
>>            End If
>>        Next
>>    End Sub
>>

>>
>>and at the txtBase level (inferring from your wise advice ...)
>>
>>

>>    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 t As DataTable = CType(B.DataSource, DataTable)
>>        Dim c As DataColumn = Nothing
>>
>>        If t Is Nothing Then
>>            Dim t1 As DataView = B.DataSource
>>            c = t1.Columns(B.BindingMemberInfo.BindingField)
>>        Else
>>            c = t.Columns(Me.DataBindings.Item(0).BindingMemberInfo.BindingField)
>>        End If
>>
>>        ' Dim o As DataColumn = cols(Me.DataBindings.Item(0).BindingMemberInfo.BindingField)
>>        Dim cT As String = c.DataType.ToString
>>        If cT = "System.String" Then
>>            Me.Mask = ">" & New String("A", c.MaxLength)
>>            Exit Sub
>>        End If
>>        If cT = "System.DateTime" Then
>>            Me.Mask = ">##/AAA/##"
>>            Exit Sub
>>        End If
>>        MsgBox(Me.Name & " cannot be masked yet (" & cT & ")")
>>    End Sub
>>

>>
>>Now this won't compile because "columns is not a member of 'system.data.dataview', and leaving out the dataview section does not work. (I don't think I need the dataview section). When I debug, B.Datasource does not seem to be set (in fact it returns "nothing", your "null" I guess?)
>>
>>I get the feeling from what I read in my frmXXX.designer.vb that the datasource of the "binding" is a dataset, whereas you seemed to assume that it should be a datatable or a dataview.
>>
>>That is precisely the problem I guess, because the form generates a xxxdataset that and binds the controls to a datatable that belongs the xxxDataset and is called XXX and referred to as xxxDataset.xxx. And it's the latter that I would like get a hold of from my base class textbox.