private void LocationBtn_Clicked(object sender, EventArgs e)
        {
            LocationModel stringInThisCell = (LocationModel)((Button)sender).BindingContext;

            System.Diagnostics.Debug.WriteLine("send  msg  current update = " + stringInThisCell.ToLocation);

            string source = stringInThisCell.ToLocation;
            string result = "XYZ";

            string[] values = { source, result };

            MessagingCenter.Send <LoadItemPutawayTemplate, string[]>(this, "Location", values);
        }
        public MainPage()
        {
            InitializeComponent();

            WorkItems = new List <LocationModel>();

            WorkItems.Add(new LocationModel {
                ToLocation = "Tomato"
            });
            WorkItems.Add(new LocationModel {
                ToLocation = "Zucchini"
            });
            WorkItems.Add(new LocationModel {
                ToLocation = "Tomato2"
            });
            WorkItems.Add(new LocationModel {
                ToLocation = "Romaine2"
            });
            WorkItems.Add(new LocationModel {
                ToLocation = "Zucchin2"
            });

            MessagingCenter.Subscribe <LoadItemPutawayTemplate, string[]>(this,
                                                                          "Location", async(sender, values) =>
            {
                string source = values[0];
                string result = values[1];
                System.Diagnostics.Debug.WriteLine("receive message current update = " + source + " -----  " + result);

                for (int i = 0; i < WorkItems.Count; i++)
                {
                    LocationModel model = WorkItems[i];
                    if (source.Equals(model.ToLocation))
                    {
                        model.ToLocation = result;
                        break;
                    }
                }
            });



            workList.ItemsSource = WorkItems;  // ItemsSource="{ Binding WorkItems}"
        }