private void btnSell_Click(object sender, EventArgs e) { try { int maxToSell = Int32.Parse(txtStock.Text); int newStock = maxToSell - Convert.ToInt32(nUDQuantity.Value); if (txtCustomerName.Text == "" || txtItemName.Text == "" || txtPrice.Text == "") { MessageBox.Show("Fill all fields correct"); } else if (Convert.ToInt32(nUDQuantity.Value) == 0 || Convert.ToInt32(nUDQuantity.Value) > maxToSell) { MessageBox.Show("Quantity must be between 1 and " + txtStock.Text); } else { store = Store.StoreInstance; Purchase purchase = new Purchase(txtCustomerName.Text, txtItemName.Text, Convert.ToDouble(txtPrice.Text), Convert.ToInt32(nUDQuantity.Value), DateTime.Parse(dateTimePurchase.Text)); bs.AddPurchase(purchase); if (itemType == "Book") { bs.SellBook(store.Id, newStock); } else if (itemType == "Journal") { bs.SellJournal(store.Id, newStock); } MessageBox.Show("You have successfully selled " + txtItemName.Text + " to " + txtCustomerName.Text); store.Display(); ClearFields(); AddItem add = AddItem.AddItemInstance; add.ClearFields(); this.Hide(); store.Hide(); store.Show(); } } catch (Exception ex) { MessageBox.Show(ex.Message); } }