Having issue binding combo-box in silverlight using WCF

     public class Appsrvvice : IAppsrvvice
     {
       
        public void DoWork()
        {
         }

        public List<fillupcombox> fillup()
        {
            List<string> x=new List<string>();
            List<string> y=new List<string>();

            string connectionstring = "server=localhost;User Id=root;password=root;Persist Security Info=True;database=mv_store";
            string msg;

             msg = "";
            MySqlConnection con = new MySqlConnection(connectionstring);
            MySqlDataAdapter ad = new MySqlDataAdapter("select Product_Name,Product_Id from product_detail Order by Product_Name", con);

            DataTable dt = new DataTable();

            try
            {
                ad.Fill(dt);
              //  return dt;

                for(int i=0;i<dt.Rows.Count;i++)
                {
                    x.Add(dt.Rows[i]["Product_Name"].ToString());
                    y.Add(dt.Rows[i]["Product_Id"].ToString());
                }

            }

            catch (Exception e)
            {

                msg = e.Message;
                return null;

            }
            finally
            {
                ad.Dispose();
            }


            return new List<fillupcombox>()
            {
                new fillupcombox()
                {
                    Texts=x,
                    Valuess=y
                }
            };
        }
    }



    [ServiceContract]
    public interface IAppsrvvice
    {

        [OperationContract]
        void DoWork();

        [OperationContract]
        List<fillupcombox> fillup();

    }

    [DataContract]
    public class fillupcombox
    {

        [DataMember]
        public List<string> Texts
        {
            get;
            set;
        }

        [DataMember]
        public List<string> Valuess
        {
            get;
            set;

        }

    }

Heres My main page code

     public MainPage()
       
     {
            InitializeComponent();

            ServiceReference1.AppsrvviceClient obj = new ServiceReference1.AppsrvviceClient();
            obj.fillupCompleted += new EventHandler<ServiceReference1.fillupCompletedEventArgs>(fillupCompletedp);
            obj.fillupAsync();
            
           

        }


        public void fillupCompletedp(object sender, ServiceReference1.fillupCompletedEventArgs e)
        {
            

             comboBox1.ItemsSource =e.Result;
          

        }