Question

I have a collection of objects that all implement one (custom) interface: IAuditEvent.

Each object can be stored in a database and a unique numeric id is used for each object type.

The method that stores the objects loops around a List<IAuditEvent>, so it needs to know the specific type of each object in order to store the correct numeric id.

Is it poor practice to have an enumeration property on IAuditEvent so that each object can identify its type with a unique enumeration value?

I can see that the simplest solution would be to write a method that translates a Type into an integer, but what if I need an enumeration of audit events for another purpose? Would it still be wrong to have my enumeration property on IAuditEvent?

Answer 1

This database type id (or discriminator) is essentially metadata of each type. Mixing data and metadata on each instance isn’t great. My preferred solution would be to write a custom attribute to hold this metadata, apply it to each type, and read these using the GetCustomAttributes method of Type.

[DatabaseDiscriminator(123)]
public class MyAuditEvent : IAuditEvent
{
}