I want show data in tree view format using Colllaapsible panel with in the repeater extender control

<asp:Repeater ID="GVCurrentClients" runat="server">
                           <HeaderTemplate>
                               <h4>
                                   <b>Current Clients</b></h4>
                               <ul>
                           </HeaderTemplate>
                           <FooterTemplate>
                               </ul>
                           </FooterTemplate>
                           <ItemTemplate>
                               <b>
                                   <asp:Panel ID="Panel1" runat="server">
                                       <asp:Label ID="lblcrpsoft" runat="server" Text='<%#"[ + ]"+Eval("NAME")%>'></asp:Label>
                                   </asp:Panel>
                               </b>
                               <ajaxToolkit:CollapsiblePanelExtender ID="Collaps" runat="server" TargetControlID="Panel2"
                                   CollapseControlID="Panel1" CollapsedText='<%#"[ + ]"+Eval("NAME")%>' ExpandControlID="Panel1"
                                   ExpandedText='<%#"[ - ]"+Eval("NAME")%>' ExpandDirection="Vertical" TextLabelID="lblcrpsoft"
                                   Collapsed="true">
                               </ajaxToolkit:CollapsiblePanelExtender>
                               <asp:Panel ID="Panel2" runat="server">

                                    <asp:Repeater ID="GVCurrentContacts1" runat="server">
                                    <HeaderTemplate>
                           <ul>
                       </HeaderTemplate>
                       <FooterTemplate>
                           </ul>
                       </FooterTemplate>
                              <ItemTemplate>
                               <li><b>
                                   <%# DataBinder.Eval(Container.DataItem, "FNAME")%>
                                  </b></li>
                               <li><b>
                                   <%# DataBinder.Eval(Container.DataItem, "EMAIL_ADDRESS")%></b></li>
                           </ItemTemplate>
                           </asp:Repeater>
                                       </asp:Panel>
                           </ItemTemplate>
                       </asp:Repeater>

                        <asp:Repeater ID="GVCurrentContacts1" runat="server">
                                    <HeaderTemplate>
                           <ul>
                       </HeaderTemplate>
                       <FooterTemplate>
                           </ul>
                       </FooterTemplate>
                              <ItemTemplate>
                               <li><b>
                                   <%# DataBinder.Eval(Container.DataItem, "FNAME")%>
                                  </b></li>
                               <li><b>
                                   <%# DataBinder.Eval(Container.DataItem, "EMAIL_ADDRESS")%></b></li>
                           </ItemTemplate>
                           </asp:Repeater>