private void addListItem()
        {
            var newItem = new ListItemViewModel()
            {
                Number = newItemNumber
            };

            newItemNumber++;
            ItemCollection.Add(newItem);
        }
        private void updateAnItem(int number)
        {
            var currVm    = ItemCollection.FirstOrDefault(vm => vm.Number == number);
            var indexOfVM = ItemCollection.IndexOf(currVm);

            ItemCollection[indexOfVM] = new ListItemViewModel
            {
                Number = currVm.Number,
                IsRead = currVm.IsRead
            };
        }
 private void removeAnItem(ListItemViewModel item)
 {
     ItemCollection.Remove(item);
 }