Using Solidworks API is there a unique identifier for the following entities:

Line, Arc, Circle, Block

I need to be able to attach properties to each of these entities. I have seen in other CAD packages that they use unique identifiers (like a hash) with a unique ID value. Is there such a value in the Solidworks API?

My plan is to use Third Party Storage Store to keep the additional attributes of these entities. I will need a key value for each of these entities.