I'm using Entity Framework for the first time, and I need to add business logic before inserting new objects into the db, here are the options I thought about:
Have a look at validation with EF - the validation is inside the entities themselves.
It's a very clean way to organise your project.
When you have POCOs, the obvious place for entity validation is in the POCO itself.
It makes sense that any validation of the Customer object is actually in the Customer class.