Repeater headertemplate find <ul> on ItemDataBound

I am trying to add an attribute to a tag with ID 'SubNav2' on ItemDataBound which is in the HeaderTemplate of a repeater.

But I keep getting the error: Object reference not set to an instance of an object.

Which i think is because it is not finding the object with ID 'SubNav2', am i going about it the correct way?

CODE BEHIND

If e.Item.ItemType = ListItemType.Header Then

        Dim ulSubNav2 As HtmlGenericControl = CType(e.Item.FindControl("SubNav2"), HtmlGenericControl)
        ulSubNav2.Style.Add("display", "block")

    End If

Additonal Code So the i'm trying to find is in the second repeater ID=reSubNav2. Does it have to have runat=server on it?

<asp:Repeater ID="reSubNav" runat="server">
    <HeaderTemplate>
        <ul>
    </HeaderTemplate>
    <ItemTemplate>
        <li><asp:HyperLink ID="SubNavLink" runat="server"></asp:HyperLink>

            <asp:Repeater ID="reSubNav2" runat="server" OnItemDataBound="reSubNav2_ItemDataBound">
                <HeaderTemplate>
                    <ul id="SubNav2" style="display:none;">
                </HeaderTemplate>
                <ItemTemplate>
                     <li><asp:HyperLink ID="SubNavLink2" runat="server"></asp:HyperLink></li>
 开发者_如何学编程               </ItemTemplate>
                <FooterTemplate>
                    </ul>
                </FooterTemplate>
            </asp:Repeater>
            <ul>
        </li>
    </ItemTemplate>
    <FooterTemplate>
        </ul>
    </FooterTemplate>
</asp:Repeater>

CODE BEHIND

    Protected Sub reSubNav2_ItemDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.RepeaterItemEventArgs)

    If e.Item.ItemType = ListItemType.Item OrElse e.Item.ItemType = ListItemType.AlternatingItem Then

        Dim rowView As System.Data.DataRowView
        rowView = CType(e.Item.DataItem, System.Data.DataRowView)

    ElseIf e.Item.ItemType = ListItemType.Header Then

        Dim ulSubNav2 As HtmlGenericControl = CType(e.Item.FindControl("SubNav2"), HtmlGenericControl)
        ulSubNav2.Style.Add("display", "block")

    End If

End Sub

Make sure that the UL has the runat="server" tag, and you should be able to find it.

EDIT

Instead of running the whole list at the server, try just running the list item at the server, like this:

<ul>
   <li id="listItem" runat="server">Hello!</li>
</ul>

If that doesn't give any errors, you should be able to access it in code behind like this:

HtmlGenericControl ctrl = e.Item.FindControl("listItem");