private void onClick(object sender, EventArgs e) { quanTextbox = Convert.ToInt16(numericUpDown1.Value); String name = ((MyButton)sender).Text; double price = ((MyButton)sender).Price; int id = ((MyButton)sender).ProductId1; // listBox1.Items.Add(snack.ToString()); if (tabControl1.SelectedTab == tabPage1) { Snack snack = new Snack(id, name, price); OrderLine orderLine = new OrderLine(holder1, quanTextbox, snack); order.AddOrderLine(orderLine); listBox1.Items.Add(orderLine.AsString()); double p = 0; foreach (OrderLine item in order.getAllOrderLines()) { p += item.Price * item.Quantity; } lbTotal.Text = "Total: € " + p; } else if (tabControl1.SelectedTab == tabPage2) { Drink drink = new Drink(id, name, price); OrderLine orderLine = new OrderLine(drink.Name, quanTextbox, drink); order.AddOrderLine(orderLine); listBox1.Items.Add(orderLine.AsString()); double p = 0; foreach (OrderLine item in order.getAllOrderLines()) { p += item.Price * item.Quantity; } lbTotal.Text = "Total: € " + p; } }