Nueman is right. Your question is too broad. Too general. You do not provide enough information. Without knowing the requirements of your application it's very hard to help you. You ask for a class or method for this application...but a class or method that does what? Are you adding or updating products in your product table? Are you placing an order from a customer? Are you placing an order to a supplier? You need to be much more specific if you want real help.
If you don't even know where to start, you should google for some basic tutorials. Google Results
The very first result is a Code Project article:Beginners guide to accessing SQL Server through C#
This should get you started. Hope it helps.