Unexpected Duplicate FK Record inserted

[ychuang-tw]

I'm kind of a Postgresql newbie here. Not sure if this is a bug or not.
Scenario:
table Author {ID, AuthorName, BirthYear}
table Books {ID, AuthorID, BookName, PublishYear}

in EF Models
there would be a "public virtual Author Author {get;set;}" statement.

in the past when I use EF for MSSQL
I would do
_book.Author=_author;
db.Authors.Add(_author);
db.Books.Add(_book);
then _book.AuthorID would be automatically filled with ID value of newly added _author record

yet in Postgresql
I find that the same behavior would cause two _author record inserted to the table, with different ID value.

I'm not sure whether there's any way to fix it?

[ychuang-tw]

I solved this by doing
//_book.Author=_author;
db.Authors.Add(_author);
_book.AuthorID=_author.ID;
db.Books.Add(_book);