// get all friends younger than 50.
            var now = DateTime.Now;
            var youngFriendsQuery =
            from friend in friends
            where (friend.BirthDate > now.AddYears(-50))
            select friend;

            // get all friends younger than 50.
            var now = DateTime.Now;
            var youngFriendsQuery =
            from friend in friends
            where (friend.BirthDate > now.AddYears(-50))
            select friend;