using Automapper with LINQ in Web Api get method

Question

I have a small Web Api method. How can I map properties in GetBooks method with Automapper? I have tried the solution here .

I have tried

 return from c in db.Books select Mapper.Map<BookDTO>(c);

But it didnt work. Here is my complete code;

     //GET: api/Books
      public IQueryable<BookDTO> GetBooks()
      {
        var books = from b in db.Books
                    select new BookDTO()
                    {
                        Id = b.Id,
                        Title = b.Title,
                        AuthorName = b.Author.Name
                    };

        return books;
    }

Book.cs

 public class Book
{
    public int Id { get; set; }
    [Required]
    public string Title { get; set; }
    public int Year { get; set; }
    public decimal Price { get; set; }
    public string Genre { get; set; }

    // Foreign Key
    public int AuthorId { get; set; }
    // Navigation property
    public Author Author { get; set; }
}

BookDTO.cs

 public class BookDTO
   {
    public int Id { get; set; }
    public string Title { get; set; }
    public string AuthorName { get; set; }
   }

thanks in advance.

You are right. I was in a hurry thats why I wrote like that. I mean I tried the methods on the link I have given. And it didnt work. I implemented this code on to mine. return from c in context.Customers select Mapper.Map(c); — oneNiceFriend, Feb 19 '16 at 16:16

score 2 · Accepted Answer · answered Feb 19 '16 at 15:40

2

Config Map between Book and BookDTO in Global.asax.cs or Startup.cs file:
```
Mapper.CreateMap<Book, BookDTO>();
```

Map db.Books in GetBooks() method:

using AutoMapper.QueryableExtensions;

...

public IQueryable<BookDTO> GetBooks()
{
    return db.Books.ProjectTo<BookDTO>();
}

answered Feb 19 '16 at 15:40

Arturo Menchaca

15,783
1
29
53

Yes, It worked, really amazing. Do you have any idea about How does Automapper knows BookDTO.AuthorName is Book.Author.Name ? – oneNiceFriend Feb 19 '16 at 16:17
@OneNiceFriend: If for any property on the destination type a property does not exist on the source type, AutoMapper splits the destination member name into individual words (by PascalCase conventions), This link explains it better: https://github.com/AutoMapper/AutoMapper/wiki/Flattening – Arturo Menchaca Feb 19 '16 at 16:26

score 1 · Answer 2 · answered Feb 19 '16 at 16:35

You need projection. See Automapper - Projection

Mapper.CreateMap<Book, BookDTO>()
    .ForMember(dest => dest.Id, opt => opt.MapFrom(src => src.Id))
    .ForMember(dest => dest.Title, opt => opt.MapFrom(src => src.Title))
    .ForMember(dest => dest.AuthorName, opt => opt.MapFrom(src => src.Author.Name));

IEnumerable<Book> books = db.Books.Cast<Book>();
// assuming Books implements IEnumerable
BookDTO result = Mapper.Map<Book, BookDTO> books;

I'm not sure if you need the projection lines for properties Id and Title. Read the documentation of AutoMapper to see what defaults it uses.

using Automapper with LINQ in Web Api get method

2 Answers2