EF avoiding fetch when Count a List - entity-framework

Question

I have a scenario where I'm trying to count items in a List. This List is a proxy coming from EF. But, when I call Count method, each item from list is fetched, and it decreases a lot the performance. Is there a way to avoid it?
Look for an example:
Domain Classes:
public class Desire
{
public virtual int Id { get; set; }
public virtual string Title { get; set; }
public virtual List<Vote> Votes { get; set; }
}
public class Vote
{
public virtual int Id { get; set; }
public virtual UserProfile User { get; set; }
public virtual DateTime DateTime { get; set; }
}
Repository:
public IQueryable<Desire> GetQuery()
{
return db.Desires;
}
Domain Service:
public IQueryable<Desire> GetDesires()
{
return repository.GetQuery();
}
ASP MVC View:
<!-- here Votes is a proxy from EF -->
<!-- When Count is called, the items are fetched decreasing the performance -->
<h2>Total Votes: #item.Votes.Count</h2>

Answer 1

Always try to use View Model instead of EF's entity. Use view model to fill your needed data on it and pass view model to view instead of model.
public class DesireViewModel
{
public int Id { get; set; }
public string Title { get; set; }
public int VotesCount{ get; set; }
// add votes themselves if you really need them
// public IEnumerable<VoteViewModel> Votes { get; set; }
}
In your action method fill DesireViewModel instead of Desire:
public ActionResult MyAction()
{
var model=_db.Desires.Select(d=>
new DesireViewModel
{
Id=d.Id,
Title=d.Title,
VotesCount=d.Votes.Count(),
});
return View(model);
}
Your view's model is now IEnumerable<DesireViewModel> instead of IEnumerable<Desire>
#model IEnumerable<.Your.Namespace.DesireViewModel>
// inside loop
<h2>Total Votes: #item.VotesCount</h2>

Answer 2

Because you are querying item.Votes with your Count funktion, EF has to fetch all items (Count() forces execution of Query before it).
The only way to not fetch all data (with materializing) would be, as far as I know, with a raw sql statement:
item.Database.SqlQuery<int>("SELECT Count(*) FROM Vote;");