Trabalhando com Accordion : Ajax

<cc1:Accordion ID="Accordion1" 
    runat="server" 
    DataSourceID="SqlDataSource1" 
    SelectedIndex="0" 
    Width="100%" 
    FadeTransitions="true" 
    FramesPerSecond="40" 
    TransitionDuration="250" 
    AutoSize="None" 
    Font-Names="Verdana" 
    Font-Size="8pt" 
    RequireOpenedPane="false" 
    SuppressHeaderPostbacks="true"> 
        <HeaderTemplate>
            <table style="width: 100%">
                <tr> 
                    <td style="background: #b8defe"> 
                        <a href="" 
                            onclick="return false;" 
                            style="color: Black; text-decoration: none">
                            <b> 
                                <asp:Label ID="lblOperacao" 
                                        runat="server" Text='<%# Eval("OPERACAO") %>'>
                                </asp:Label> 
                                <%--<%# Eval("OPERACAO") %>--%> 
                                <asp:Label ID="ltrHeader" runat="server"></asp:Label>
                            </b> 
                            <%-- <%# Eval("titulo") %>--%> 
                        </a>
                    </td> 
                </tr> 
            </table> 
        </HeaderTemplate> 
    <ContentTemplate> 
        <%# retornaValor(Eval("OPERACAO"))%>
        <asp:GridView 
            ID="GridView1" 
            runat="server" 
            AutoGenerateColumns="False" 
            ShowHeader="False" 
            CellPadding="4" 
            Font-Names="Verdana" 
            Font-Size="8pt" 
            ForeColor="#333333" 
            GridLines="None" 
            Width="100%" 
            DataSourceID="SqlDataSource2">
            <FooterStyle BackColor="#507CD1" Font-Bold="True" ForeColor="White" />
            <RowStyle BackColor="#EFF3FB" /> 
            <PagerStyle BackColor="#2461BF" ForeColor="White" HorizontalAlign="Center" />
            <SelectedRowStyle BackColor="#D1DDF1" Font-Bold="True" ForeColor="#333333" />
            <HeaderStyle BackColor="#507CD1" Font-Bold="True" ForeColor="White" /> 
            <EditRowStyle BackColor="#2461BF" /> 
            <AlternatingRowStyle BackColor="White" /> 
        </asp:GridView> 
    </ContentTemplate> 
</cc1:Accordion> 
<asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:CSSGConnectionString %>" SelectCommand="SP_MENU_OPERACAO" SelectCommandType="StoredProcedure">
</asp:SqlDataSource>
<asp:SqlDataSource ID="SqlDataSource2" runat="server" ConnectionString="<%$ ConnectionStrings:CSSGConnectionString %>" SelectCommand="SP_MENU_SUBOPERACAO" SelectCommandType="StoredProcedure"> 
    <SelectParameters> 
        <asp:Parameter Name="OPERACAO" Type="String" />
    </SelectParameters> 
</asp:SqlDataSource>

 protected string retornaValor(object operacao) 
 { 
    //string valor = operacao.ToString(); 
    //carregaGrid(valor); 
    valor_retorno = null; 
    SqlDataReader dr; 
    SqlCommand cmd = new SqlCommand("SP_MENU_SUBOPERACAO", getConn()); 
    cmd.Parameters.Add("@OPERACAO", SqlDbType.VarChar, 255).Value = operacao; 
    cmd.CommandType = CommandType.StoredProcedure; 
    cmd.Connection.Open(); 
    dr = cmd.ExecuteReader(); 
    valor_retorno += string.Empty; 
    while (dr.Read()) 
    { 
        valor_retorno = "" + dr["SUBOPERACAO"].ToString().Trim() + "";  
        cmd.Connection.Close(); 
        dr.Close(); 
        return valor_retorno; 
    }
}