I've been using mysql for a while now at my internship, and I'm wondering if there's a difference between declaring if your
var result = (from r in db.table1 orderby r.datetime select r)
var result = (from r in db.table1 orderby r.datetime ascending select r)
ORDER BY is sorted in ascending order, so I guess there are no differences between your requests.
From this documentation:
ASC Optional -- It sorts the result set in ascending order by expression (default, if no modifier is provider).
DESC Optional -- It sorts the result set in descending order by expression.