WP - How to edit selected product in windows phone using php?

<StackPanel Margin="20,0,0,0" HorizontalAlignment="Left" Width="200" >
                                                <Button Height="70" Content="EDIT" Tag="{Binding product_id}" Name="btnEdit" Foreground="White" FontWeight="Medium" BorderBrush="#57842c" BorderThickness="2,0,2,0" Margin="-18,0,0,0" Click="Edit">
                                                    <Button.Background>
                                                        <ImageBrush ImageSource="Images/submit_bg.png" Stretch="Fill"  />
                                                        
                                                    </Button.Background>
                                                </Button>
                                            </StackPanel>

private void Edit(object sender, RoutedEventArgs e)
        {
           
           Button btnEdit = (Button)e.OriginalSource;
           NavigationService.Navigate(new Uri("/EditWatchList.xaml?scustomerID=" + btnEdit.Tag.ToString() + "," + sretailer_id, UriKind.Relative));
        }

rivate void MainPage_Loaded(object sender, System.Windows.RoutedEventArgs e)
        {
            string url = "http://www.bestinuk.com/BestinUk_Windows/getProductID.php";
            Uri uri = new Uri(url, UriKind.Absolute);
            NavigationContext.QueryString.TryGetValue("scustomerID", out strproductID);

            StringBuilder postData = new StringBuilder();
            postData.AppendFormat("{0}={1}", "customer_id", HttpUtility.UrlEncode(LoginPage.strcustomer_id_k));
            postData.AppendFormat("&{0}={1}", "product_id", HttpUtility.UrlEncode(strproductID));
            postData.AppendFormat("&{0}={1}", "retailer_id", HttpUtility.UrlEncode(InputList.sretailer_id));

            WebClient client = default(WebClient);
            client = new WebClient();
            client.Headers[HttpRequestHeader.ContentType] = "application/x-www-form-urlencoded";
            client.Headers[HttpRequestHeader.ContentLength] = postData.Length.ToString();

            client.UploadStringCompleted += client_UploadStringCompleted;
            client.UploadProgressChanged += client_UploadProgressChanged;

            client.UploadStringAsync(uri, "POST", postData.ToString());

            prog = new ProgressIndicator();
            prog.IsIndeterminate = true;
            prog.IsVisible = true;
            prog.Text = "Loading....";
            SystemTray.SetProgressIndicator(this, prog);
        }
        private void client_UploadProgressChanged(object sender, UploadProgressChangedEventArgs e)
        {
            //Me.txtResult.Text = "Uploading.... " & e.ProgressPercentage & "%"
        }
        private void client_UploadStringCompleted(object sender, UploadStringCompletedEventArgs e)
        {
           
            if (e.Cancelled == false && e.Error == null)
            {
                Member myMember = ReadToObject(e.Result.ToString());
                this.targetPrices.Text = myMember.target_price.ToString();
                this.txtretailers.Text = myMember.retailer.ToString();
                this.txtperiod.Text = myMember.period.ToString();
                this.txtmobile.Text = myMember.mobile.ToString();
                prog.IsVisible = false;
            }
        }
        public static Member ReadToObject(string json)
        {
            Member deserializedMember = new Member();
            MemoryStream ms = new MemoryStream(Encoding.UTF8.GetBytes(json));
            DataContractJsonSerializer ser = new DataContractJsonSerializer(deserializedMember.GetType());
            deserializedMember = ser.ReadObject(ms) as Member;
            ms.Close();
            return deserializedMember;
        }