Entity Framework 4 and Linq: OrderBy a field nested in a Query : refactor my code

Question

First, Thomas Levesque had a good solution for ordering fields in a related table where the relation may not always be there:

userQuery = userQuery.OrderBy(u => 
    (u.Department != null) ? u.Department.Name : String.Empty);

I need to do the same thing. My aggregate root is enormous:

myQuery = myQuery.OrderBy(p =>
  (p.Seconds == null
    ? 0
    : p.Seconds.FirstOrDefault() == null
      ? 0
      : p.Seconds.First().Thirds == null
        ? 0
        : p.Seconds.First().Thirds.FirstOrDefault() == null
          ? 0
          : p.Seconds.First().Thirds.First().Forths == null
            ? 0
            : p.Seconds.First().Thirds.First().Forths.FirstOrDefault() == null
              ? 0
              : p.Seconds.First().Thirds.First().Forths.First().myField));

Is this really the way to do this, or is there something much easier to read? My other problem is that the nested myField has a matching "default" value sitting in the top level Query, also named by myField. The idea was to Order by the coalesce of these two fields (??).

Edit: I think this would include the "default value" from the first field:

myQuery = myQuery.OrderBy(p =>
  (p.Seconds == null
    ? p.myDefaultField // Used to be zero
    : p.Seconds.FirstOrDefault() == null
      ? p.myDefaultField
      : p.Seconds.First().Thirds == null
        ? p.myDefaultField
        : p.Seconds.First().Thirds.FirstOrDefault() == null
          ? p.myDefaultField
          : p.Seconds.First().Thirds.First().Forths == null
            ? p.myDefaultField
            : p.Seconds.First().Thirds.First().Forths.FirstOrDefault() == null
              ? p.myDefaultField
              : p.Seconds.First().Thirds.First().Forths.First().myField));

How could I rewrite this OrderBy to be cleaner? This code fails with an error of "Cannot compare elements of type 'System.Collections.Generic.IEnumerable`1'. Only primitive types (such as Int32, String, and Guid) and entity types are supported."

Well, maybe you should be trying to solve this problem somewhere else. Are you sure you need to navigate through four relations? Can't you change the database and/or mappings so you get the data in a more apropriate format? — R. Martinho Fernandes, Nov 22 '10 at 05:18
I can always add a view and/or stored procedure, but the end result is a hierarchical JSON object going to the client. So I would end up recreating a hierarchy from a flattened object. — Zachary Scott, Nov 22 '10 at 05:25

score 2 · Answer 1 · answered Nov 22 '10 at 09:32

I think you have a pretty nasty code smell going on here, but working with what you have got I wouldn't handle this in a LINQ query like that. Just for the sake of readability I'd do something like

myQuery = myQuery.OrderBy(p =>
  (p.HasValidFields()
    ? p.Seconds.First().Thirds.First().Forths.First().myField
    : p.myDefaultField
  ));

And inside of p's class

private bool HasValidFields
{
  get
  {
    return p.Seconds != null &&
           p.Seconds.FirstOrDefault() != null &&
           .... ;
  }
}

Entity Framework 4 and Linq: OrderBy a field nested in a Query : refactor my code

1 Answers1