private void btnAddBill_Click(object sender, EventArgs e) { lblInfo.Text = ""; int addingQty = 0; if (txtQtySold.Text != "") { addingQty = Convert.ToInt32(txtQtySold.Text); } if (txtBillName.Text != null) { StockItem tempStockItem = inventory.findByName(txtBillName.Text); if (tempStockItem == null) { lblInfo.Text = "Item is not in inventory, can't add to bill"; return; } else if (tempStockItem.InStockQty >= addingQty) { BillItem addingBillItem = new BillItem(); addingBillItem.Code = tempStockItem.Code; addingBillItem.Name = tempStockItem.Name; addingBillItem.setPrice(tempStockItem.UnitPrice); addingBillItem.setQuantitySold(addingQty); bill.AddBillItem(addingBillItem); RefreshData(); } else { lblInfo.Text = "Can't add more than stock quantity"; } } else { lblInfo.Text = "Item is not in inventory, can't add to bill"; } }