When is OrderBy operator called? - linq

Question

1)
a)
var result1 = from artist in artists
from album in artist.Albums
orderby album.Title,artist.Name
select new { Artist_id = artist.id, Album_id = album.id };
Is the above query translated into:
var result = artists.SelectMany(p => p.albums
.Select(p1 => new { Artist = p, Album = p1 }))
.OrderBy(p2 => p2.Album.Title)
.ThenBy(p3 => p3.Artist.Name)
.Select(p4 => new { Artist_id = p4.Artist.id, Album_id = p4.Album.id });
b)
I'm not sure if this question will make much sense - If my assumptions are correct and thus OrderBy is always one of the last operators to get called ( when using query expression ), then how would we express the following code using query expression (in other words, how do we specify in a query expression that we want OrderBy operator to get called sooner and not as one of the last operators ):
var result = artists
.SelectMany(p1 => p1.albums
.OrderBy(p2=>p2.title)
.Select(p3 => new { ID = p3.id, Title = p3.title }));
2) Do in the following query expression the two orderby clauses get translated into OrderBy(... artist.Name).OrderBy( ... album.Title):
var result1 = from artist in artists
from album in artist.Albums
orderby artist.Name
orderby album.Title
select new { ...};
thank you

Answer 1

For question 1: orderby gets called wherever you show it. Your query isn't quite equivalent to what you showed, but it's close. It doesn't help that you formatted it so that it looks like the Select is called on the result of SelectMany, when it's actually on the arguments to SelectMany. Your query is translated to something more like:
var result = artists
.SelectMany(artist => artist.albums, (artist, album) => new {artist, album})
.OrderBy(z => z.album.Title)
.ThenBy(z => z.artist.Name)
.Select(z => new { Artist_id = z.artist.id, Album_id = z.album.id }
Question 1b) Your query is roughly equivalent to:
var result = from p1 in artists
from p3 in (from p2 in p1.albums
orderby p2.title
new { ID = p2.id, Title = p2.title })
select p3;
It's only a rough translation as nothing in query expressions is converted to that overload of SelectMany, as far as I can remember. On the other hand, it could be that this does what you want in a slightly simpler way:
var result = from p1 in artists
from p3 in p1.albums.OrderBy(p2 => p2.title)
select new { ID = p3.id, Title = p3.title };
You'll still get the ordering within the artist. It's a mixture of query expression and "dot notation", but it looks good to me. Odd that you're not using p1 in the final result, mind you...
For question 2, using two orderby clauses you do indeed get two OrderBy calls, which is almost certainly not what you want. You want:
var result1 = from artist in artists
from album in artist.Albums
orderby artist.Name, album.Title
select new { ...};
That gets translated into the appropriate OrderBy(...).ThenBy(...) calls.