This tutorial will teach you  to make a small Fish shop Inventory  system using c#.net. The following  system will use to manage the Fish shop. paste the code inside the ok button string status = txtstatus.SelectedItem.ToString(); double qty = double.Parse(txtqty.Text); if(status.Equals("KG")) { double tot = qty * 140; txtbill.Text = tot.ToString(); } else { double tot = qty/1000 * 140; …