InvoiceDetailsViewModel GetProductFromHiddenGridView()
        {
            GridViewRow             row  = SelectedProductGridView.Rows[0];
            InvoiceDetailsViewModel item = new InvoiceDetailsViewModel
            {
                ProductID = row.FindLabel("ProductId").Text.ToInt(),
                ItemName  = row.FindLabel("ItemName").Text,
                Price     = row.FindLabel("ItemPrice").Text.ToDecimal(),
                Quantity  = QuantityTextBox.Text.ToInt(),
                Amount    = row.FindLabel("ItemPrice").Text.ToDecimal() * QuantityTextBox.Text.ToInt()
            };

            return(item);
        }