Binding Dropdown get values from DB

        public void Dropdownlist2()//gridvalues1_RowDataBound(object sender, GridViewRowEventArgs e)
        {
            try
            {
                SqlConnection con = new SqlConnection(ConnectionString);
                //con.Open();
                string str = "select month,week from duration";
                SqlCommand cmd = new SqlCommand(str, con);
                con.Open();
                SqlDataAdapter da = new SqlDataAdapter();
                // DataSet ds = new DataSet();
                DataTable dt = new DataTable();
                da.SelectCommand = cmd;
                da.Fill(dt);
                DropDownList2.DataSource = dt;
                DropDownList1.DataTextField = "month";
                // DropDownList1.DataValueField = "Title";
                DropDownList2.DataValueField = "month";
                DropDownList2.DataBind();
            }
            catch (Exception ex)
            {
                throw (ex);
            }
        }