private static void AddOfferConfirmButton_Click(object sender, RoutedEventArgs e) { DataModels database = DataModels.GetInstance(); Button button = (Button)sender; List <object> data = (List <object>)button.Tag; ComboBox websiteCombo = (ComboBox)data[0]; ComboBox HotelCombo = (ComboBox)data[1]; ComboBox RoomCombo = (ComboBox)data[2]; TextBox priceText = (TextBox)data[3]; Website website = (Website)websiteCombo.SelectedItem; Room room = (Room)RoomCombo.SelectedItem; int price = int.Parse(priceText.Text); bool done = database.AddOffer(new Offer(website, room, price)); if (done) { MessageBox.Show("Offer Added successfully !"); } else { MessageBox.Show("Couldn't add offer"); } }