public SoilStructureViewModel(INavigation navigation, SOIL _soil)
{
_navigation = navigation;
_thissoil = _soil;
ListGrade = PickerService.GradeItems().ToList();
ListKind = PickerService.KindItems().ToList();
ListClass = PickerService.ClassItems().ToList();
ClearCommand = new Command(() => ClearItems());
SetCalc();
}