visible labels

hi every one

I have 2 label in my page and 2 button i write this code in behind code for my buttons

 protected void imgarticle_Click(object sender, ImageClickEventArgs e)
    {

        lblmanager.Visible = false;
        lblclasspro.Visible = true;

    }

and

 protected void IMGmanage_Click(object sender, ImageClickEventArgs e)
    {
 lblmanager.Visible = true;       
 lblclasspro.Visible = false;
       
    }

when i click on one of button it worked but when i click other button in second tim this error occur

Databinding methods such as Eval(), XPath(), and Bind() can only be used in the context of a databound control.

this is my label code

 1-lblclasspro

 <asp:Label ID="lblclasspro" runat="server" Text="Label" Visible="false">
               <div id="Dclass">
            <div id="Dcs">
                <asp:Label ID="Label5" runat="server" Text="Label" CssClass="MainLabel">Product</asp:Label>
                </div>
            </div>
            <div id="Dcenters">
            <div id="DLinkp">
                <asp:LinkButton ID="LinkButton3" runat="server" CssClass="Links"> view Product</asp:LinkButton></div>
            <div id="Dlinks">
                <asp:Image ID="Image4" runat="server" ImageUrl="~/image/arrow.png" /></div>
            <br />
            <div>
                <asp:DataList ID="DLclass" runat="server">
                    <ItemTemplate>
                       
                        <table class="style1">
                            <tr>
                                <td class="TdLinks">
                                    <asp:LinkButton ID="Linkbtnclass" runat="server" CssClass="Links1" 
                                        onclick="Linkbtnclass_Click" CommandArgument='<%# Eval("Name") %>'><%# Eval("Name") %></asp:LinkButton>
                                </td>
                                <td class="TDILinks">
                                    <asp:Image ID="Image3" runat="server" ImageUrl="~/image/arrow.png" />
                                </td>
                            </tr>
                        </table>
                       
                    </ItemTemplate>
                </asp:DataList>
                </div>
            </div>
            <div id="Dbuttons"></div>
                </asp:Label>

and

 2-lblmanager

 <asp:Label ID="lblmanager" runat="server" Text="Label" Visible="true">
                <div id="DMmanager">
               <div id="DMlink1">
                    <div id="DLinkp1">
                    <asp:LinkButton ID="LinkproM" runat="server" CssClass="Links2"> Manager</asp:LinkButton></div>
                     <div id="Dlinks1">
                    <asp:Image ID="Imgarrow" runat="server" ImageUrl="~/image/arrow.png" /></div>
                </div>

why this error occure?

thanks