A DevExpress ASPxNavBar is, I think, a bar one may click to make an expandable area expand into view or collapse away from view.

<dx:PanelContent>
   <dx:ASPxNavBar ID="MyNav" runat="server" EnableCallBacks="true" Width="100%"
         ClientInstanceName="MyNav" RenderMode="Lightweight">
      <ClientSideEvents EndCallback="Whatever" />
      <GroupContentTemplate>
         <asp:Panel ID="WorkFlowTemplatePanel" runat="server">
         </asp:Panel>
      </GroupContentTemplate>
   </dx:ASPxNavBar>
</dx:PanelContent>