When I tried to focus on compiler in code i made break point on code if (!IsPostBack) { using (SqlConnection Con = Connection.GetConnection()) {

            if (Request.QueryString["Category_Id"] != null && DDlProductFamily.SelectedIndex < 0)
            {
                SqlCommand Com = new SqlCommand("SelectAllCtageories_Front", Con);
                Com.CommandType = CommandType.StoredProcedure;
                Com.Parameters.Add(Parameter.NewInt("@Category_Id", Request.QueryString["Category_Id"]));

                SqlDataAdapter DA = new SqlDataAdapter(Com);
                DA.Fill(dt);
                DataList1.DataSource = dt;
                DataList1.DataBind();
            }

but I cannot check condition although I had the value of query string

1. List item