how to create array of panels in vb.net asp

Question

I need 3 panels. Instead of manually name this panels I want an array of panels? how can I do this in VB.net and ASP

in my ASP page I have

<asp:Panel ID="Panel1" runat="server"></asp:Panel>

Then in VB.net I generate an array of panels. which will be added to Panel1. This is what I have so far (inside a loop)

Dim DivPanel() As Panel = Nothing
For i = 0 To 2
   DivPanel(i) = new panel
   DivPanel(i).controls.add(txtBox)
   Panel1.controls.add(DivPanel(i))
Next

I got an error at "DivPanel(i) = new panel" . The error is "NullReferenceException was caught"

please advice... thank you thank you very much

Answer 1

You get the error because you've declared the array but you haven't initialized it here:

Dim DivPanel() As Panel = Nothing

However, you don't need that array at all:

For i = 0 To 2
   Dim panel = new Panel()
   Dim txtBox = new TextBox()
   panel.controls.add(txtBox)
   Panel1.controls.add(panel)
Next

Note that i have also created one TextBox for every panel, you cannot use the same instance.

Remember to recreate dynamically created control on every postback with the same ID as before in Page_Load at the latest. Threfore you need to know how many controls were already created. You could use the ViewState to persist the number.

Recommandable readings:

• TRULY Understanding Dynamic Controls
• Page-Lifecycle

Or you use one of the builtin Data-Bound Control like Repeater that do this automatically. You only have to set their DataSource and call DataBind ().

Here are answers of me on similar questions with implementations:

• C#
• VB.NET (+ C#)