Dynamically change the number of header cells in listview LayoutTemplate - asp.net

Question

I'm trying to dynamically create a listview. on reports.aspx user selects a bunch of checkboxes. On the next page, user sees reports.aspx, and should see a table with columns of the checkboxes he selected. My idea was to create a listview, then dynamically change the header row of the LayoutTemplate, then change the select statement depending on which columns selected. This is what I have:
<asp:ListView runat="server" ID="ReportListView" DataSourceID="ReportListViewSDS">
<LayoutTemplate runat="server">
<table runat="server">
<tr runat="server">
<%
' Doesn't work because code blocks (<%%>) aren's allowed inside <LayoutTemplate> blocks
'For Each i As String In Request.Form
'Response.Write("<th>" & Request.Form(i) & "</th>")
'Next
%>
</tr>
</table>
<asp:PlaceHolder runat="server" ID="itemPlaceHolder" />
</LayoutTemplate>
...
Problem is that this doesn't work because i can't put a code block (<%%>) inside the LayoutTemplate. Is there a way in the code behind to edit the LayoutTemplate, or another way to cycle through the Request.Form vars and build the table header row with it?
Thanks for any advice/direction!
-Russ

Answer 1

Try using the ItemTemplate for the binding syntax instead of the layout template. I believe the layout template is strictly for layout.
Also, it looks like you're using classic ASP code blocks. ASP.NET code blocks look like this:
For data binding:
<%# Eval("<COLUMN NAME>")%>
For other cases not involving data binding:
<%= Request.QueryString["Hello"] %>

Answer 2

Since the control is already a server side control, try giving the and id and then modifying the header on pre-render:
<asp:ListView runat="server" ID="ReportListView" DataSourceID="ReportListViewSDS">
<LayoutTemplate runat="server">
<table runat="server">
<tr id='trCustomHeader" runat="server">
Then in your code behind, attach this logic to the listview's pre-render
ReportListView_PreRender(...)
{
TableRow tr = ReportListView.FindControl("trCustomerHeader");
TableCell tempCell = new TableCell();
tempCell.Text = ...
tr.Cells.Add(tempCell);
}

Answer 3

I just created a separate table on the page, outside of the listview, that was the simple way of doing it.
<asp:Table ID="HeaderTable" runat="server">
<asp:TableHeaderRow ID="HeaderTableHeaderRow" runat="server" />
</asp:Table>
<asp:ListView ...>
...
</asp:ListView>
Then in the code behind:
For Each i As String In Request.Form
If i.IndexOf("checkbox_") = 0 Then
Dim c As New TableHeaderCell()
Dim l As New LinkButton()
l.Text = i.Substring(Len("checkbox_"))
c.Controls.Add(l)
c.CssClass = "customreport"
HeaderTableHeaderRow.Cells.Add(c)
End If
Next
Pretty simple. So I didn't have to use a LayoutTemplate at all.