C# Entity Framework populate partial property

Question

I have an entity called Person who has a collection of addresses.

I created:

public partial class Person
{
     public int AddressCount{get{return Addresses.Count;}}
}

This returns the error:

The ObjectContext instance has been disposed and can no longer be used for operations that require a connection.

I am returning a collection of people, how can I do this without doing this:

public int AddressCount
        {
            get
            {
                using (var c = new Entities())
                {
                    return c.People.Where(s => s.PersonId == PersonId).Single().Addresses.Count;
                }
            }
        }

Why don't you want to do 'this' ?

Kirk Broadhurst
– Kirk Broadhurst

2011-02-01 00:44:04 +00:00
Commented Feb 1, 2011 at 0:44 — Kirk Broadhurst
– Kirk Broadhurst, Commented Feb 1, 2011 at 0:44

Matt Hamilton · Accepted Answer · 2011-02-01 07:55:44Z

4

I've found that this works to eager-load a "count" property without loading all the entities in the collection:

using (var context = new Entities())
{
    var people = (from p in c.People
                  select new 
                  {
                      Person = p,
                      AddressCount = p.Addresses.Count
                  }).ToList();

    foreach (var item in people)
    {
        item.Person.AddressCount = item.AddressCount;
    }
}

The drawback, of course, is that AddressCount needs to be settable. I guess you could give it an internal setter if your context is in the same assembly as the entity class.

You may not need the Include("Addresses") on there - that's worth testing. Edit removed it since it's not necssary (and may in fact make the query do more work than it has to).

edited Feb 1, 2011 at 7:55

answered Feb 1, 2011 at 0:40

Matt Hamilton

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3 Comments

RPM1984 Over a year ago

beat me by about 15 seconds.. +1

Matt Hamilton Over a year ago

@RPM1984 Do you remember if the Include() call is necessary?

RPM1984 Over a year ago

since your projecting (to an anonymous type), no - it's not necessary, EF will get what it needs automatically.

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