Entity Framework搜索指定字段解决方案

public class Book
{
        [Key]
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int Id { get; set; }

        [Required, MaxLength()]
        public string Title { get; set; }
        public Double? Price { get; set; }
}

解决方案一：

var bkList = db.Books.Select(allBooks => new { Id = allBooks.Id, Title = allBooks.Title }).Select(b => new Book { Id=b.Id,Title=b.Title});

解决方案二：

var bkList2 = db.Books.Select(allBooks => new { Id = allBooks.Id, Title = allBooks.Title }).ToList().ConvertAll<Book>(b => new Book(){ Id=b.Id,Title=b.Title});

解决方案三：

//声明一个与Book一模一样的克隆类
public class BookClone
{
    public int Id { get; set; }

    public string Title { get; set; }

    public Double Price { get; set; }
}

var bkList3 = db.Books.Select(allBooks => new BookClone { Id = allBooks.Id, Title = allBooks.Title });

这三种方案都可以解决The entity or complex type '{0}' cannot be constructed in a LINQ to Entities query. 的异常