Why doesn't this work ? (control array)

Hello everybody,


I'm creating a control array which I need to make on certain moment visible or not.

Right now the only controls in my ctl array are labels. If I want to make them visible, I want to use in my ShowInvoice sub a loop to loop through my control array.
Everything works fine ... only if I use

VB Code:

typeof sInvoice(i) is label then
sInvoice(i).visible=true
end if

If I just use sInvoice(i).visible = true (without the typeof condition) then I receive Object reference not set to an instance of an object :(
I don't want to change my showinvoice routine each time when there's a new kind of control in my array !

I really don't see why this is happening !

Hope someone can help me out !

This is my code (this doesn't work => but I want this one to work)

VB Code:

Private Function InvoiceArray()
 
        Dim sInvoice(20) As Control
 
        sInvoice(1) = lblInvoiceTo
        sInvoice(2) = lblInvoiceName
        sInvoice(3) = lblInvoiceAddress
        sInvoice(4) = lblInvoiceNr
        sInvoice(5) = lblInvoiceZip
        sInvoice(6) = lblInvoicePlace
 
        Return sInvoice
 
    End Function
 
Private Sub ShowInvoice()
        Dim sInvoice() As Control
        Dim i As Integer
        sInvoice = InvoiceArray()
 
        Dim ctl As Control
        For i = 0 To UBound(sInvoice)
            sInvoice(i).Visible = True
        Next

This doesn't work

VB Code:

For i = 0 To UBound(sInvoice)
            sInvoice(i).Visible = True
            If TypeOf sInvoice(i) Is Label Then
                sInvoice(i).Visible = True
                Response.Write(sInvoice(i).GetType.ToString)
            End If
        Next

Ok, ok, I got it ! :(

I needed to check my control on nothing ....
This code works great now :

VB Code:

Private Function InvoiceArray()
 
        Dim sInvoice(20) As Control
 
        sInvoice(1) = lblInvoiceTo
        sInvoice(2) = lblInvoiceName
        sInvoice(3) = lblInvoiceAddress
        sInvoice(4) = lblInvoiceNr
        sInvoice(5) = lblInvoiceZip
        sInvoice(6) = lblInvoicePlace
 
        Return sInvoice
 
    End Function
 
Private Sub ShowInvoice()
        Dim sInvoice() As Control
        Dim i As Integer
        sInvoice = InvoiceArray()
 
        Dim ctl As Control
        For i = 0 To UBound(sInvoice)
            if not sinvoice(i) is nothing then
               sInvoice(i).Visible = True
            end if
        Next
End sub

If you wanted to shorten your code you could do this:

VB Code:

Private Function InvoiceArray()
 
        Dim sInvoice() As Control = {lblInvoiceTo, lblInvoiceName, lblInvoiceAddress, lblInvoiceNr, lblInvoiceZip, lblInvoicePlace}
        Return sInvoice
    End Function
 
    Private Sub ShowInvoice()
        Dim sInvoice() As Control= InvoiceArray()
 
        Dim ctl As Control
        For Each ctl In sInvoice
            If Not ctl Is Nothing Then
                ctl.Visible = True
            End If
        Next
    End Sub

Functionally it is no different, other than the sInvoice array being a dynamic size instead of 20 elements. It just has a few shortcuts to save space.

Indeed Edneis,



this is in fact a wonderfull tip !
You gave me in a few lines more to understand then I already read in lots of books and newsgroups !

Thanks a lot !

Bjorn