具有密钥（PK）的实体不会往返

Question

I have two tables: <subjects> and <prerequisites> . The primary key of prerequisite table is a composite key: pr_subject_id and pr_prerequisite_subject_id . They are both foreign keys from the <subjects> table. I can map the pr_subject_id in a association but i can't map the return trip ( pr_prerequisite_subject_id ). See image. How should i solve this?

note : When i made the associations in sql server it was fine but when i loaded the database in the entity framework, the entity framework dropped the prerequisite table because of this return trip association.

Answer 1

I looked around but i think this is a common problem with the Entity Framework. I found two workarounds here . Basically what i did was adding a third column er_id and let that be the primary key. Then to enforce that there will be no double of the other two columns i added a unique constraint.