求救----怎样在GridView把层的ID改变~~~~~~~

怎样在GridView里面加一个层呀  <asp:TemplateField HeaderText="操作">
    <ItemTemplate>                            
     <input type="button" id="btn" onclick='document.getElementById("<%="divShow"+i %>").style.display = document.getElementById("<%="divShow"+i %>").style.display=="none"?"":"none";'/>
     <div id='<%="divShow"+i %>' style="position:absolute;z-index:20px;display:none">                 
      <table>
        <%#(i=i++) %>
          <tr>
            <td><asp:Label ID="lblAssetID" runat="server" Text='<%#DataBinder.Eval(Container.DataItem, "a_Id")%>' /></td>
                      </tr>
                      <tr>                                                
                        <td>所属的主资产</td>
                       </tr>
                       <tr>
                        <td><asp:TextBox ID="tbAssetID" runat="server"/></td>                        
                      </tr>
                      <tr>
                        <td>
                          <asp:Button ID="btnSubmit" runat="server" CommandName="delete" Text="确定" />
                        </td>
                      </tr>
                    </table>
                  </div>
                 </ItemTemplate>
                 <ItemStyle Width="60px" />
                 </asp:TemplateField>我这样子写的话，每次出来的都是第一个ID的层，选第二个也是第一个ID的层,怎样才能让div的ID变得不一样呢？