public ListItemViewModel(INavigationService navigationService, IPageDialogService dialogService, IRepositoryService repository) : base(navigationService, dialogService)
{
_service = new ListItemService(this, repository);
AddCommand = new DelegateCommand(async() => await _service.OpenItem(null));
EditCommand = new DelegateCommand <Item>(async(item) => await _service.OpenItem(item.Id));
DeleteCommand = new DelegateCommand <Item>(async(item) => await _service.DeleteItem(item.Id));
SearchCommand = new DelegateCommand(async() => await _service.Load(SearchText));
}