private async void Initialize()
        {
            collection_GiaoDan = new ObservableCollection <ChiTietGiaoDanViewModel>();

            await Task.Run(() =>
            {
                //ListGiaoHo = new ObservableCollection<string>(DiaChiServices.GetListGiaoHo());
                //ListGioi = new ObservableCollection<string>(new List<string>
                //{ "Thiếu Nhi","Giới Trẻ","Gia Trưởng","Hiền Mẫu","Cao Niên" });
                var list = GiaoDanServices.GetAllActiveGiaoDan();
                foreach (var gd in list)
                {
                    var _vm          = new ChiTietGiaoDanViewModel();
                    _vm.ID           = gd.ID;
                    _vm.TenThanh     = gd.TenThanh;
                    _vm.NgaySinh     = gd.NgaySinh;
                    _vm.Ho           = GiaoXuHelper.SplitLastName(gd.HoTen);
                    _vm.Ten          = GiaoXuHelper.SplitFirstName(gd.HoTen);
                    _vm.NgThgNamsinh = GiaoXuHelper.UnionDayMonthYear(gd.NgaySinh, gd.ThangSinh, gd.NamSinh);

                    _vm.GioiTinh    = gd.GioiTinh;
                    _vm.GiaoHo      = gd.GiaoHo;
                    _vm.Gioi        = gd.Gioi;
                    _vm.SoDienThoai = gd.SoDienThoai;

                    collection_GiaoDan.Add(_vm);
                }
            });

            App.Current.Dispatcher.Invoke((Action) delegate
            {
                ListGiaoDan = CollectionViewSource.GetDefaultView(collection_GiaoDan);
                ListGiaoDan.SortDescriptions.Add(new SortDescription("Ten", ListSortDirection.Ascending));
            });
        }
        private async void AddGiaoDan(object obj)
        {
            _vm = new ChiTietGiaoDanViewModel();
            //let's set up a little MVVM, cos that's what the cool kids are doing:
            var view = new ThemGiaoDan();

            //show the dialog
            var result = await DialogHost.Show(view, "RootDialog", ClosingEventHandler);

            if ((int)result != 0)
            {
                collection_GiaoDan.Add(_vm);
            }
        }