Setting active tab in ASP.NET Ajax TabContainer causes entire container to disappear

Question

I have an ASP.NET page that uses the ASP.NET Ajax Control Toolkit TabContainer. In the Page_Load event, I am hiding some of the tabs based on the data given to the page. I then want to make one of the tabs active based on the value of an (optional) query string parameter.

So I have:

protected void Page_Load ( object sender, EventArgs e )
{
    if ( !this.IsPostBack )
    {
        // Tabs with no data are hidden in here
        LoadDataIntoTabs();

        PreselectCorrectTab();
    }
}

private void PreselectCorrectTab ()
{
    if ( ctlTabContainer.Visible )
    {
        if ( !string.IsNullOrEmpty( Request.QueryString[ "tabIndex" ] ) )
        {
            int tabIndex = 0;

            if ( int.TryParse( Request.QueryString[ "tabIndex" ], out tabIndex ) )
            {
                if ( ( ctlTabContainer.Tabs.Count > tabIndex ) && ctlTabContainer.Tabs[ tabIndex ].Visible )
                {
                    ctlTabContainer.ActiveTabIndex = tabIndex;
                }
            }
        }
    }
}

If I hit the page with the tabIndex query string parameter set, the entire tab container disappears.

The strange thing is that if I change LoadDataIntoTabs() to not hide tabs that contain no data, everything works as you would expect (i.e. the correct tab is selected when the page renders).

Any ideas?

---

EDIT

As requested, here are more details:

private void LoadDataIntoTabs ()
{
    LoadPendingWidgetsTab();
    LoadDataIntoTab2();
    LoadDataIntoTab3();
    // etc...
}

private void LoadPendingWidgetsTab ()
{
    IList<Widget> pendingWidgets = GetAllPendingWidgets();

    if ( ( pendingWidgets != null ) && ( pendingWidgets.Count > 0 ) )
    {
        tbpPendingWidgets.Visible = true;
        tbpPendingWidgets.HeaderText = String.Format( "Pending Widgets ({0})", pendingWidgets.Count );

        grdPendingWidgets.DataSource = pendingWidgets;
        grdPendingWidgets.DataBind();
    }
    else
    {
        tbpPendingWidgets.Visible = false;
    }
}

Answer 1

Can it be that it doesn't count the hidden Tabs and therefore selects the wrong tab?

Answer 2

Try to set the desired tab via ActiveTab like:

ctlTabContainer.ActiveTab = tbpPendingWidgets;

If you set the first tab to Visible=false then you have to set the next visible tab page via ActiveTab.

I'am using the AjaxControlToolkit Release 30930 (September 2009).