Refractoring a nested query in Linq to Entity Framework

Question

Supposing I have this query:

var ps = from p in dc.Products
         let text =
             (from t in p.Text
              orderby t.Language == "ja" descending
              select t).FirstOrDefault()
         select new { p.Id, text.Name };

Is there any way to refractor the query being assigned to text?

My guess is that I need to make it an Expression<Func<Product, string, ProductText>>, but I don't know how I'd invoke it.

By the way, if there are more efficient ways to do this, I'd be happy to know.

Thanks,

Rei

Edit: To clarify, the idea is that if Japanese isn't available, I want it to fall back on whatever other language is available.

Maybe this is more efficient?

let text = p.Text.FirstOrDefault(t => t.Language == "ja") ?? p.Text.FirstOrDefault()

Either way, my main question is about how I might make text query reusable -- because it's rather unintuitive, and I can picture myself or someone else doing it wrong in the future.

Ian Mercer · Accepted Answer · 2010-11-04 06:07:42Z

1

EDITED BASED ON COMMENT

var ps = dc.Products.Select(p => new 
{
    Id = p.Id, 
    Text = p.Text.OrderBy(t=> t.Language == "ja").First()
})
.Select (x => new
{
    Id = x.Id,
    Name = x.Name,
    ...
});

edited Nov 4, 2010 at 6:07

answered Nov 4, 2010 at 5:39

Ian Mercer

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3 Comments

Rei Miyasaka Over a year ago

Not quite, because I want it to fall back on whatever language is available. Also, it's likely that I'll be wanting more than just Name -- hence the let.

Ian Mercer Over a year ago

Makes sense, although I suspect you'd really want to fall back to a specific language rather than some random one?? How about the edited version then? Although now it's pretty much identical to what you started with.

Rei Miyasaka Over a year ago

Hmm yeah, that looks quite close to my first one. I'm guessing the executed query is pretty much the same. Falling back to a particular language would be good (probably English), but I'll probably worry about that later if I ever end up with a third language. Should be able to just add a then by fallbackPriority or something along those lines. Right now I'm only worried about Japanese and English.

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