BooksController-DetailsAction

            var book = (from theBook in _context.Books.Where(b => b.BookId == id)
                        join loan in _context.BookLoans.Where(x => !x.ReturnedOn.HasValue) on theBook.BookId equals loan.BookID into result
                        from loanWithDefault in result.DefaultIfEmpty()
                        select new BookDetailsViewModel
                        {
                            BookID = theBook.BookId,
                            SubTitle = theBook.SubTitle,
                            Title = theBook.Title,
                            Author = theBook.Author,
                            ISBN = theBook.ISBN,
                            GenreName = theBook.Genre.Name,
                            DeweyName = theBook.Dewey.Name,
                            StudentID = loanWithDefault.StudentID,
                            IsAvailable = loanWithDefault == null,
                            AvailableOn = loanWithDefault == null ? (DateTime?)null : loanWithDefault.DueOn
                        }).FirstOrDefault();