how to fetch particular record from 1 datalist to 2nd datalist

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ASP.NET

i have created 2 datalist 1'st is catalogue & 2'nd is cat_detail

now my que is in catalogue i select pizza in 2'nd datalist which is cat_detail i want only pizza records

in detail

catalogue tbl=cat_id,cat_nm for ex:1,pizza
2,pasta
cat_detail tbl=id,cat_id,name,type,price,des. 
for ex:1,1,margherita pizza,veg,200,abc.
2,1,mashroom riot,veg,200,xyz
3,2,italian pasta,veg,150,pqr

code is like that..
catalogue.aspx

<asp:DataList ID="DataList2" runat="server" DataKeyField="cat_id"
           RepeatColumns="1"  BackColor="White"
           BorderColor="#E7E7FF" BorderStyle="None" BorderWidth="1px"
          CellPadding="10" Font-Bold="True" Font-Italic="True" Font-Size="X-Large"
          Font-Underline="True" ForeColor="Black" ItemStyle-BorderColor="#FF9933"
          ItemStyle-Font-Bold="True" ItemStyle-ForeColor="#FF9933"
          SelectedItemStyle-ForeColor="White" SelectedItemStyle-BackColor="#FF9933"
          GridLines="Horizontal" onselectedindexchanged="DataList2_SelectedIndexChanged">

         <ItemTemplate>
             <asp:LinkButton ID="LinkButton1" runat="server"  onclick="LinkButton1_Click" Text='<%#Bind("cat_nm") %>' CausesValidation="True">LinkButton</asp:LinkButton>
          <!--<asp:Label ID="lbl_catalogue_name" runat="server"></asp:Label><br />-->

      </ItemTemplate>
       </asp:DataList>
    </div>
  </div></td>

 <td>
 <div class="right-content1"><center>
  <div class="title2"><center> your menu..</center></div>
  <div id="#right-content">
      <asp:ValidationSummary ID="ValidationSummary1" runat="server"
          ShowMessageBox="True" ShowSummary="False" />


      <asp:DataList ID="DataList1" runat="server" DataKeyField="id"
           RepeatColumns="3"  BackColor="White"
           BorderColor="#E7E7FF" BorderStyle="None" BorderWidth="1px" CellPadding="3"
           GridLines="Horizontal"
          onselectedindexchanged="DataList1_SelectedIndexChanged">

         <ItemTemplate>
             Catalogue Name:
          <asp:Label ID="idLabel" runat="server" Text='<%# Eval("name") %>'></asp:Label><br />
             Type:
          <asp:Label ID="cat_idLabel" runat="server" Text='<%# Eval("type") %>'></asp:Label><br />
          <asp:Image ID="Image1" runat="server" ImageUrl='<%#Bind("image")%>' Height="200px" Width="200px"/><br />
             Price:
          <asp:Label ID="typeLabel" runat="server" Text='<%# Eval("price") %>'></asp:Label>

          <asp:ImageButton ID="ImageButton1" onclick="ImageButton1_Click" runat="server" ImageUrl="images/saddtocart2.gif" height="30px" width="80px" align="right"/>
                 <h4><a href="detail.aspx?id=<%# Eval("id") %>" >More</a></h4>
                <br /><br />
      </ItemTemplate>
       </asp:DataList>

catalogue.aspx.cs

protected void Page_Load(object sender, EventArgs e)
    {
        connection c1 = new connection();    
        DataList2.DataSource=c1.selval("select * from catalogue");
        DataList2.DataBind();
        
        
    }
    protected void ImageButton1_Click(object sender, ImageClickEventArgs e)
    {
        
        Response.Redirect("shippingcart.aspx");
    }

    protected void DataList1_SelectedIndexChanged(object sender, EventArgs e)
    {
        
    }
    protected void DataList2_SelectedIndexChanged(object sender, EventArgs e)
    {
       
    }
    protected void LinkButton1_Click(object sender, EventArgs e)
    {
        
        SqlConnection con = new SqlConnection(@"Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\Database.mdf;Integrated Security=True;User Instance=True");
        SqlDataAdapter sda = new SqlDataAdapter("select * from cat_detail where cat_id=1", con);
        DataSet ds = new DataSet();
        sda.Fill(ds);
        DataList1.DataSource = ds;
        DataList1.DataBind();
    }

from this code i get only pizza detail not pasta or other cataloguemenu