Func<T,T> 委托 与 lambda 使用

    public class Book
    {
        public int BookId { get; set; }
        [Required]
        public string Title { get; set; }
        public decimal Price { get; set; }
        public string Genre { get; set; }
        public DateTime PublishDate { get; set; }
        public string Description { get; set; }
        public int AuthorId { get; set; }
        [ForeignKey("AuthorId")]
        public Author Author { get; set; }

    }

    public class BookDto
    {
        public string Title { get; set; }
        public string Author { get; set; }
        public string Genre { get; set; }
    }

private static readonly Expression<Func<Book, BookDto>> AsBookDto =
            x => new BookDto
            {
                Title = x.Title,
                Author = x.Author.Name,
                Genre = x.Genre
            };

public IQueryable<BookDto> GetBooks()
        {
            return db.Books.Include(b => b.Author).Select(AsBookDto);
        }