Question

Table name: Author

• AuthorID -> primary key
• FirstName
• LastName

Table name: Titles

• ISBN -> primary key
• BookTitle
• EditionNumber
• CopyRight

Table name: AuthorISBN

• ISBN -> foreign key
• AuthorID -> foreign key

I can do:

var AuthorsAndISBNs =
            from author in database.Author
            join books in database.AuthorISBN
                on author.AuthorID equals books.AuthorID
            orderby author.LastName, author.FirstName
            select new { author.FirstName, author.LastName, books.ISBN };

However, I cannot do:

var authorsAndTitles =
           from title in database.Titles
           from book in title.AuthorISBN
           let author = book.Author
           orderby author.LastName, author.FirstName, title.BookTitle
           select new { author.FirstName, author.LastName, title.BookTitle };

I thought LINQ automatically creates properties based on foreign-key relationships, which enables you to easitly access related rows in other tables:(

Author has one-to-many relationship with AuthorISBN which has ‘many-to-one’ relationship with Titles

Please help! been stuck on this for days:'( THANK YOU!

Answer 1

In Order for LINQ let you access related rows in other tables, every table MUST have a PrimaryID. The issue was that ‘AuthorISBN’ Table did not have a primaryID, therefore no properties were being created:)