private void GetSubGroup()
{
List <string> tempList = ListProducts.Select(x => x.ProductGroup).OrderBy(x => x).ToList();
tempList = tempList.Distinct().ToList();
SubGroup = tempList.Where(s => s.Substring(0, 2).Contains(SelectedMainGroup)).ToList();
SubGroup = SubGroup.Select(x => x.Substring(3)).ToList();
NotifyPropertyChanged("");
}