/// <summary>
        /// Add the selected item from the UpDownListView
        /// </summary>
        public void Add()
        {
            if (ListItems == null || ListItems.Count == 0)
            {
                return;
            }

            if (AvailableListItems == null)
            {
                AvailableListItems = new ObservableCollection <ListItem>();
            }

            var selectedIndex = 0;
            var count         = ListItems.Count;

            for (int j = 0; j < count; j++)
            {
                selectedIndex = count - j - 1;
                ListItem item = ListItems[selectedIndex];

                if (item.IsSelected == false)
                {
                    continue;
                }

                AvailableListItems.Add(item);
                ListItems.Remove(item);
            }
        }
        /// <summary>
        /// Add all items from the UpDownListView
        /// </summary>
        public void AddAll()
        {
            if (ListItems == null || ListItems.Count == 0)
            {
                return;
            }

            if (AvailableListItems == null)
            {
                AvailableListItems = new ObservableCollection <ListItem>();
            }

            int count = ListItems.Count;

            for (int i = 0; i < count; i++)
            {
                var item = ListItems[0];
                ListItems.RemoveAt(0);
                AvailableListItems.Add(item);
            }
        }