public void Execute(object parameter)
        {
            List <User> users = new List <User>();

            try
            {
                users = new List <User>(App.DB.UserRepository.GetAllData());
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
            SaleViewModel saleViewModel = new SaleViewModel()
            {
                AllSales = App.DB.SaleRepository.GetAllData()
            };

            try
            {
                saleViewModel.ClientViewModel = new ClientViewModel();
                var clients = App.DB.ClientRepository.GetAllData();
                saleViewModel.ClientViewModel.AllClients = clients;
            }
            catch (Exception)
            {
            }
            Book book = new Book();

            book = BookViewModel.SelectedBook;
            try
            {
                saleViewModel.CurrentSale = new Sale()
                {
                    Book         = book,
                    Client       = saleViewModel.ClientViewModel.SelectedClient,
                    SaleDateTime = DateTime.Now,
                    Note         = "",
                    No           = 1,
                    RealPrice    = book.PurchasePrice,
                    SalePrice    = book.SalePrice,
                    Id           = 1,
                    User         = BookViewModel.CurrentUser
                };
            }
            catch (Exception)
            {
            }
            SaleWindow saleWindow = new SaleWindow(saleViewModel);

            saleWindow.ShowDialog();
        }