问题
I've got a custom OData feed that for books. Each book can have multiple authors and an author can be involved in multiple books so I implemented this using a join table (Book - BookAuthorJoin - Author). My proxy object has Book.BookAuthorJoins BookAuthorJoin.Books & BookAuthorJoin.Authors.
What I want todo is have a single query where I get all the books for an author in a single LINQ query, but having trouble applying the filter. Seems I want two Expand() methods, but that isn't working. The following query doesn't work, but shows what I'm trying to do:
var query = from book in ODataContext.Books.Expand("BookAuthorJoins").Expand("Authors")
where book.BookAuthorJoins.Author.AuthorID = authorID
select book;
回答1:
On the server side, the 1-to-many or many-to-many relationship is usually exposed as just a navigation property, exposing the join table in the middle will make your life much harder. If you use EF you should be able to hide the table and just expose the relationship as a navigation property. In any case, to get all books for a certain author the query should look like:
/Authors(123)/Books
The result of this query is just a feed of books.
If you do keep the join table exposed then something like this migth work:
/Authors(123)/BookAuthorJoins?$expand=Book
But this time you get all the BookAuthorJoins with the Book for each as well.
来源：https://stackoverflow.com/questions/4441665/use-linq-for-double-nested-odata-collection