Problem with Hyperlink in ASP.Net DataList control

I am trying to make a vertical menu bar. I am getting the categories using data list from table cat_details. In that data list there is another datalist in <li> where when i pause shpuld display the sub categories relative to the datalist1 category i hover upon. The css part is right, but i cant figure out the querystring of datalist2. Please help or suggest an alternate.

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CODE :

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<asp:DataList ID="DataList1" runat="server" DataSourceID="SqlDataSource1" 

         DataKeyField="cat_name">

     <ItemTemplate>

     <ul><li>

         <asp:HyperLink ID="HyperLink3" Cssclass="hyper" runat="server" Text='<%#Eval("cat_name") %>'></asp:HyperLink>

         <ul> <li>

             <asp:DataList ID="DataList2" runat="server" DataSourceID="SqlDataSource2">

             <ItemTemplate>

                 <asp:HyperLink CssClass="sub" ID="HyperLink4" runat="server" Text='<%#Eval("sub_name") %>'></asp:HyperLink>

             </ItemTemplate>

             </asp:DataList></li></ul>

     </li></ul>

     </ItemTemplate>

     </asp:DataList>

     <asp:SqlDataSource ID="SqlDataSource1" runat="server" 

         ConnectionString="<%$ ConnectionStrings:classifiedsConnectionString %>" 

         SelectCommand="SELECT * FROM [cat_details]"></asp:SqlDataSource>

     <asp:SqlDataSource ID="SqlDataSource2" runat="server" 

         ConnectionString="<%$ ConnectionStrings:classifiedsConnectionString %>" 

         SelectCommand="SELECT [sub_name] FROM [sub_details] WHERE ([cat_name] = @cat_name)">

         <SelectParameters>

             <asp:ControlParameter ControlID="DataList1" Name="cat_name" 

                 PropertyName="SelectedValue" Type="String" />

         </SelectParameters>

     </asp:SqlDataSource>

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li:hover ul { display: block; }

li ul { display:none;}