public TextbooksDetailViewModel(MTextbook item, TextbooksViewModel vm)
        {
            bool isNew = item.ID == 0;

            this.item = item;
            this.vm   = vm;
            item.CopyProperties(ItemEdit);
            LANGNAME      = vm.vmSettings.SelectedLang.LANGNAME;
            ItemEdit.Save = ReactiveCommand.CreateFromTask(async() =>
            {
                ItemEdit.CopyProperties(item);
                if (isNew)
                {
                    await vm.Create(item);
                }
                else
                {
                    await vm.Update(item);
                }
            });
        }