You can't add values to an enum at runtime, that's impossible in .NET, so it's also impossible with CodeFluent.

So, you want to create another entity that will store the list of enums. That would be a 1:M relation. This is how you would layout that relation:

Each enumeration value would be a row in the ProductType table. With CodeFluent, you can declare "instances" for an entity that will become rows in the final table, so here, you can declare your initial enum values using instance, so use the instance grid on the ProductType entity, and add instances:

Note in this case, maybe you want to create the ProductType's Id property as an int without identity (if you don't want those enum int values generated by the database).