This question is based on a [email protected] MVC Application.
I have the following function which should return a List of some class I made. Does anyone know how I can translate the IQueryable to a list? I have tried ToList(). But it still gives me a convert error.
Cannot implicitly convert type ‘System.Collections.Generic.List<>’ to ‘Model.Book[]’ [firstChance-2nd-attempt]csharp(CS0029)
LibraryController.cs
[HttpGet("GetAuthorsAndBooks")]
public AuthorBooks[] GetAuthorsAndBooks()
{
//TODO 6: missing code 1pt
var authorsAndBooks = (
from a in _context.Authors
let bookList = (
from ba in _context.BookAuthor
where ba.AuthorId == a.Id
join b in _context.Books on ba.BookId equals b.Id
select new { Id = b.Id, Title = b.Title, Year = b.Year }
)
select new AuthorBooks { Author = a, Books = bookList.ToList() }
);
return authorsAndBooks; // ! CONVERT ERROR
}
public class AuthorBooks
{
public Author Author { get; set; }
public Book[] Books { get; set; }
}
Thanks to @Phong it works. See the modified LibraryController.cs below.
LibraryController.cs [solution]
[HttpGet("GetAuthorsAndBooks")]
public AuthorBooks[] GetAuthorsAndBooks()
{
//TODO 6: missing code 1pt
var authorsAndBooks = (
from a in _context.Authors
let bookList = (
from ba in _context.BookAuthor
where ba.AuthorId == a.Id
join b in _context.Books on ba.BookId equals b.Id
select new Book { Id = b.Id, Title = b.Title, Year = b.Year }
)
select new AuthorBooks { Author = a, Books = bookList.ToArray() }
).ToArray();
return authorsAndBooks;
}
public class AuthorBooks
{
public Author Author { get; set; }
public Book[] Books { get; set; }
}
Answer
You have 2 ways to get rid of the error
Declare
Listinstead ofArraytypepublic class AuthorBooks { public Author Author { get; set; } public List<Book> Books { get; set; } }Books = bookList.ToArray()instead.
Updated
You are selecting anonymous type at here
select new { Id = b.Id, Title = b.Title, Year = b.Year }
So you should select new Book instead, Like this
select new Book { Id = b.Id, Title = b.Title, Year = b.Year }