Brtdku

Hey I have structure which looks like this:

Those are 2 libraries which have some data inside and also list of books called "books".

Inside of my Library controller I'm filling context with mocked data like:

public LibrariesController(LibrariesContext context)

    {

        _context = context;



        if (_context.Libraries.Count() == 0)

        {

            // Create a new TodoItem if collection is empty,

            // which means you can't delete all TodoItems.

            _context.AddRange(getMockedLibraries());



            _context.SaveChanges();

        }

    }

Methods for mocking data just add some static content to this context like:

private List<Book> getMockedBooks()

    {

        List<Book> mockedBooks = new List<Book>();



        Book newBook = new Book();

        newBook.Title = "Pride and Prejudice (Paperback)";

        newBook.Author = "Jane Austen";



        mockedBooks.Add(newBook);



        newBook = new Book();

        newBook.Title = "To Kill a Mockingbird (Paperback)";

        newBook.Author = "Harper Lee";



        mockedBooks.Add(newBook);



        return mockedBooks;

    }



    private List<Library> getMockedLibraries()

    {



        List<Library> mockedLibraries = new List<Library>();







        Library newLibrary = new Library();



        newLibrary.Name = "ZUT Library";

        newLibrary.ImgSrc = "http://przemysl-40.pl/wp-content/uploads/logo_ZUT.jpg";

        newLibrary.Books = getMockedBooks();



        mockedLibraries.Add(newLibrary);



        newLibrary = new Library();



        newLibrary.Name = "US Library";

        newLibrary.ImgSrc = "http://partner.kubg.edu.ua/images/stories/Partners/poland1.jpg";

        newLibrary.Books = getMockedBooks();



        mockedLibraries.Add(newLibrary);



        return mockedLibraries;



    }

My LibrariesContext is based on DBContextOptions and has Libraries DbSet inside:

public class LibrariesContext : DbContext

{

    public LibrariesContext(DbContextOptions<LibrariesContext> options)

        : base(options)

    {

    }



    public DbSet<Library> Libraries { get; set; }

    public DbSet<Book> Books { get; set; }

}

The funniest part happen when I go to the /api/Libraries endpoint and want to see bueatifull JSON on my site second time, implementation looks like:

// GET: api/Libraries

    [HttpGet]

    public async Task<ActionResult<IEnumerable<Library>>> GetTodoItems()

    {

        return await _context.Libraries.ToListAsync();

    }

I'm a beginner with a .NetCore and I can't understand why after second request to the same endpoint I got some nulls in place of books list like:

I would be really grateful for any advice.

In your GET request, your query is only returning Libraries. Try eager loading the Books so that they are joined in the query and included in the results:

// GET: api/Libraries 

[HttpGet] 

public async Task<ActionResult<IEnumerable<Library>>> GetTodoItems() 

{ 

    return await _context.Libraries.Include(l => l.Books).ToListAsync(); 

}

change return await _context.Libraries.ToListAsync(); to

 return await _context.Libraries.Include(x => x.Books).ToListAsync();