I have a CheckBoxList that I am trying to validate that at least one of the checkboxes is checked.

Markup:

<asp:CustomValidator ID="RequiredFieldValidator8" ValidationGroup="EditArticle" runat="server" ErrorMessage="At least one Category is required." OnServerValidate="topic_ServerValidate" />
            <asp:CheckBoxList id="checkboxlistCategories" runat="server"></asp:CheckBoxList>

Code-behind:

protected void topic_ServerValidate(object source, ServerValidateEventArgs args)
        {
            int i = 0;
            foreach (ListItem item in checkboxlistCategories.Items)
            {
                if (item.Selected == true)
                    i = i + 1;
            }
                if (i == 0)
                    args.IsValid = false;
                else
                    args.IsValid = true;
        }

If I add ControlToValidate="checkboxlistCategories" in the CustomValidator control, it blows up! Am I missing something?

Thanks in advance.