Javascript to show/hide panel but panel may not be visible on page load

Hi
I have a user control, say called
MyUserControl

MyUserControl has a panel on it, panel1, and a combobox, NumberUnits

Depending on the value of "NumberUnits" (0-5) , Panel1 must be shown/hidden.


If numberUnits = 0, Panel1 should be hidden
else   panel1 should be shown


On page_load, the "NumberUnits" combobox is set to a value in session, say Session("NumberUnits")

On a page using master page I have two instances of these.  MyUserControl1 & MyUserControl2

On page_load of the MyUserControl I add javascript to the NumberUnits combobox like so. This means on changing the combobox, the panel is shown/hidden.
               js.Append("showHidePanel(")
                js.Append(Panel1.ClientID)
                js.Append(",")
                js.Append(NumberUnits.ClientID)
                js.Append(")")
                Me.NumberUnits.Attributes.Add("onchange", js.ToString)

HOWEVER there is a problem.

IF Panel1 is set to be hidden on loading, it is not rendered and so where the onchange event takes place nothing happens.

How do I get over this?
There are two things:
1) Panel1 must be able to be shown/hidden on changing NumberUnits combobox
2) Panel1 must be able to be shown/hidden on page load  [so it needs to be rendered even if not visible on page load]

Hope this makes sense.

Thansk in advance for assisting with code....hopefully I'm not way off with what I've done so far...
function showHidePanel(panel, unitsChosen)
    {
        // show the panel
        if (unitsChosen.value>0)
        {
            alert(unitsChosen.value);
            panel.style.visibility = "visible";
            
        }
        else
        {
            // hide the panel
            alert(unitsChosen.value);
            panel.style.display = "none"; //to hide it
        }    
    }

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rwallacejAsked:
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tiagosalgadoConnect With a Mentor Commented:
Instead of yourpanel.Visible = false, try to use yourpanel.Style.Add("visible","hidden")
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rwallacejAuthor Commented:
thank you very much, for the benefit of others this works:

in .ascx.vb
                If NumberUnits.SelectedIndex = 0 Then
                    Panel1.Style.Add("visibility", "hidden")
                End If
 
in .ascx javascript
    function showHidePanel(panel, unitsChosen, model, iso, isoAmbient)
    {
        // show the panel
        if (unitsChosen.value>0)
        {
            panel.style.visibility = "visible";
        }
        else
        {
            // hide the panel
            panel.style.visibility = "hidden";
        }    
    }

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0
 
tiagosalgadoCommented:
glad to help! Accept the solution pls.
0
 
rwallacejAuthor Commented:
thanks - I got interrupted and forgot to accept solution
0
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