Returning a CollapsiblePanelExtender over/through ajax/javascript

Question

I would like to be able to return a programmatically generated collapsible panel extender through javascript along with it's panel and so on. I've got the panel and associated tables going through just fine however when I try and attach the cpe it breaks. and returns an error:

The cpe panel and such are being generaged by a WebService and I'm trying to get JS to write what the webservice returns to a particular field dynamically

Microsoft JScript runtime error: Sys.Net.WebServiceFailedException: The server method 'Sub_Menu_Helper' failed with the following error: System.InvalidOperationException-- Page cannot be null. Please ensure that this operation is being performed in the context of an ASP.NET request.

    {
     Label somelabel = new Label();
     somelabel.ID = somenumber.ToString();
     somelabel.Text = somenumber.ToString();
     subpnlContent.Controls.Add(somelabel);
     ++somenumber;
    }

    CollapsiblePanelExtender cpeMenuLast = new CollapsiblePanelExtenderEx();
    cpeMenuLast.ID = "subcpe" + strMenuId + strParentHierarchyIds;
    cpeMenuLast.TargetControlID = "subpnlContent" + strParentMenuId + "_" + strMenuId;
    cpeMenuLast.ExpandControlID = "cellContent" + strParentMenuId + "_" + strMenuId;
    cpeMenuLast.CollapseControlID = "cellContent" + strParentMenuId + "_" + strMenuId;
    cpeMenuLast.Collapsed = bCollapsed;
    cpeMenuLast.TextLabelID = strMenuName;
    cpeMenuLast.ExpandedText = m_strButtonLabelHide;
    cpeMenuLast.CollapsedText = m_strButtonLabelShow;
    cpeMenuLast.ImageControlID = "imglnk" + strMenuId;
    cpeMenuLast.CollapsedImage = "~/App_Themes/default/nbExpand.gif";
    cpeMenuLast.ExpandedImage = "~/App_Themes/default/nbCollapse.gif";
    cpeMenuLast.SuppressPostBack = true;
    cpeMenuLast.ScrollContents = false;

    //Add Everything
    cellSubMenu.Controls.Add(subpnlContent);
    cellSubMenu.Controls.Add(cpeMenuLast);
    row.Cells.Add(cellSubMenu);
    tbl.Rows.Add(row);

    using (StringWriter sw = new StringWriter(sb))
    {
     using (HtmlTextWriter tw = new HtmlTextWriter(sw))
     {
      tbl.RenderControl(tw);
     }
    }

How can I fix this?

Answer 1

Looks like you need a Page object with a ScriptManager to render the CollapsiblePanelExtender, which makes sense since you need some script for it to work properly.

So maybe you can try the following way to render your table:

var page = new Page();
page.Controls.Add(new ScriptManager());
page.Controls.Add(tbl);
var writer = new StringWriter();
HttpContext.Current.Server.Execute(page, writer, false);
return writer.ToString();

Oliver