Can you add metadata to a folder in a document library?

I am making a visual webpart for SharePoint 2010 that displays files and folders from a document library, and I want to keep ordering to folders. I want to be able to sort folders so I need a way to store the order number of a folder. If I check on sharepoint in the browser, I don't see a way to add any info to it.

Is there a way to do this programatically in c#?

I want to avoid keeping the order number as a part of the folder name, something like: "1. Folder A"

Does anyone know if this is possible?