Question

Imagine a class like this:

public class MyEntity : Entity
{
    public virtual States States { get; set; }
}

[Flags]
public enum States
{
    None,
    State1 = 1,
    State2 = 2,
    State3 = 4,
    State4 = 8
}

I want to map it to this table:

TABLE MY_ENTITY
ID: PK
STATES_ID : FK to MY_ENTITY_STATES

TABLE MY_ENTITY_STATES
ID: PK
IS_STATE1_SET (bit)
IS_STATE2_SET (bit)
IS_STATE3_SET (bit)
IS_STATE4_SET (bit)

Is this possible?

This is a legacy scenario, I can’t change the database.

---

As per request, here is some sample data:

Table MY_ENTITY

ID | STATES_ID
---+----------
14 | 35

Table MY_ENTITY_STATES

ID | IS_STATE1_SET | IS_STATE2_SET | IS_STATE3_SET | IS_STATE4_SET
---+---------------+---------------+---------------+--------------
35 | 0             | 1             | 0             | 1

This should lead to a value of States.State2 | States.State4 in the States property in the MyEntity instance with the ID 14.

Answer 1

This is a two step solution.

First, use join to bring the MY_ENTITY_STATES record, and then write a IUserType that converts the flags to columns.

Check here for an example.