Populate Dropdown on the basis of another in SSRS

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)

        {

            SqlDataAdapter da;

            DataSet ds = new DataSet();

            try

            {

                

                da = new SqlDataAdapter("select book_Id, book_name from book where category_name = '" +                                                                        DropDownList1.SelectedItem.Text + "'", "your connection string");

                da.Fill(ds);

                DropDownList2.DataTextField = "bokk_name";

                DropDownList2.DataValueField = "book_Id";

                DropDownList2.DataSource = ds.Tables[0];

                DropDownList2.DataBind();

            }

            catch (Exception)

            {

                

                throw;

            }

        }