Cannot add an entity with a key that is already in use (LINQ)

Question

I get this error Cannot add an entity with a key that is already in use. when I run the code below.

Tables:

Answer 1

Seems you are missing primary key or an unique key on CMSPageObject table. Please try to verify the keys in the database. I had same issue since I had missed the PK on the table.

Cheers.