i find solution
var _books = (from _b in db.Books
select new
{
_b.bookAuthor,
_b.bookCountry,
_b.BookID,
_b.bookName,
_b.bookTranslator,
_b.bookImage,
_b.bookPrice,
_b.bookTotalTime,
_b.Category,
chapters = from _ch in _b.Chapters
select new
{
_ch.ChapterId,
_ch.chapterName
}
});
this solve me problem.