In my line of business we have Products. These products can be modified by a user by adding Modifications to them. Modifications can do things such as alter the price and alter properties of the Product. This, to me, seems to fit the Decorator pattern perfectly.

Now, envision a database in which Products exist in one table and Modifications exist in another table and the database is hooked up to my app through the Entity Framework. How would I go about getting the Product objects and the Modification objects to implement the same interface so that I could use them interchangeably?

For instance, the kind of things I would like to be able to do: Given a Modification object, call .GetNumThings(), which would then return the number of things in the original object, plus or minus the number of things added by the modification.

This question may be stemming from a pretty serious lack of exposure to the nitty-gritty of EF (all of my experience so far has been pretty straight-forward LOB Silverlight apps), and if that's the case, please feel free to tell me to RTFM.

Thanks in advance!