private void buttonAddToList_Click(object sender, EventArgs e) { Order order = new Order(); if (OrderValidation.isValidID(textboxOrderId) && OrderValidation.isValidClient(textboxClientId) && OrderValidation.isValidBooks(textboxBookId) && OrderValidation.isValidValues(textboxbQuantity)) { order.OrderID = Convert.ToInt32(textboxOrderId.Text); order.ClientID = Convert.ToInt32(textboxClientId.Text); order.BookID = Convert.ToInt64(textboxBookId.Text); order.Quantity = Convert.ToInt32(textboxbQuantity.Text); OrderDA.Add(order); ClearAll(); } }