public void addWeightItem(weightItem newWeightItem)
        {
            //add a to-do list item to the data context
            allWeightDB.weightList.InsertOnSubmit(newWeightItem);

            //submit changes to database
            allWeightDB.SubmitChanges();

            //add weight into the weight collection
            AllWeightItems.Add(newWeightItem);
        }
        public void deleteWeightItem(weightItem weightItemtoBeDeleted)
        {
            //remove weight item from weight collection
            AllWeightItems.Remove(weightItemtoBeDeleted);

            //remove weight item from data context
            allWeightDB.weightList.DeleteOnSubmit(weightItemtoBeDeleted);

            //save the changes to the database
            allWeightDB.SubmitChanges();
        }
        private void appbarSubmitButton_Click(object sender, EventArgs e)
        {
            //confirm there is some text in the text box
            if (weightBox.Text.Length > 0)
            {
                weightItem item = new weightItem
                {
                    Weight = weightBox.Text,
                    DateofMeasurement = newWeightDate.Value.Value.ToShortDateString()
                };
                //add the item to the viewmodel
                App.ViewModel.addWeightItem(item);

                //return to the main page
                if (NavigationService.CanGoBack)
                {
                    NavigationService.GoBack();
                }
            }
        }