how to get bind all the values in drop down depending upon the other drop down

DataClassesDataContext Db = new DataClassesDataContext();
   protected void Page_Load(object sender, EventArgs e)
   {
       if (!IsPostBack)
       {
           var result = from x in Db.cates
                        select x;

           DropDownList1.DataSource = result;
           DropDownList1.DataTextField = "cate1";
           DropDownList1.DataValueField = "id";
           DropDownList1.DataBind();

           var resultItem = from x in Db.Items
                        select x;

           DropDownList2.DataSource = resultItem;
           DropDownList2.DataTextField = "Item_name";
           DropDownList2.DataValueField = "item_code";
           DropDownList2.DataBind();


       }



   }
   protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
   {
       var result = (from x in Db.Items
                    where x.item_code == Convert.ToInt32(DropDownList1.SelectedValue)
                    select x).Single();
//put here as much as u want to bind ddl but make sure u bind ddlist in Load first  then assign SelectedValue .

       DropDownList2.SelectedValue = result.item_code.ToString();

   }

<div>
      <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True"
          onselectedindexchanged="DropDownList1_SelectedIndexChanged">
      </asp:DropDownList>
      <asp:DropDownList ID="DropDownList2" runat="server">
      </asp:DropDownList>

  </div>