OrderBy doesn't work if ThenInclude uses (or how to order nested collection)

Steps to reproduce

There is no docs found about ordering nested collection (ThenInclude() should be used), but found some fresh samples which should work (based on discussion).

Hence using the same approach the following code should sort nested items, but it doesn’t (no exception thrown):

var res = _db.Set<ApplicationUser>()
                .OrderBy(u => u.Blogs.OrderBy(b => b.Posts.OrderBy(p => p.PostOrder).First().PostOrder))
                .Include(u => u.Blogs)
                    .ThenInclude(b => b.Posts)
                .Single(u => u.Id == userId);

Further technical details

EF Core version: 1.1.2 Database Provider: Doesn’t work on both Microsoft.EntityFrameworkCore.SqlServer and Npgsql.EntityFrameworkCore.PostgreSQL (this is the main one) Operating system: Windows 7 / Mac OS X 10.12.6 IDE: VS Code / Visual Studio 2017

[maumar]

Include only determines which navigations are going to be loaded in the final projection. For your scenario you can try ordering on the client:

var res = _db.Set<ApplicationUser>()
	.Include(u => u.Blogs)
	.ThenInclude(b => b.Posts)
	.Where(u => u.Id == userId)
        .ToList()
        .Select(u => u.Blogs.OrderBy(b => b.Posts.OrderBy(p => p.PostOrder).First().PostOrder))
        .Single();

If you want to sort on the server, then you would have to construct the projection manually (i.e. Include can’t be used for this) - and this currently would produce a separate query to fetch Posts for each Blog (which is potentially very slow)

[smitpatel]

closing as Duplicate of #9067