Using The DataContext In EntityFramework To Retrieve Nested Objects

I’m always somewhat amazed when I read something from documentation that is not straight forward and it actually works. So amazed and excited that I often feel the need to blog about it.

So, here is the problem. I created a CodeFirst implementation of EntityFramework in Visual Studio and created a simple hierarchy in my data model. That is, without showing all the code, here is what I have:

public class Person
{
    [Key]
    [DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }

    public virtual List<EmailAddressInfo> EmailAddressInfoList { get; set; }
    ..
}

public class EmailAddressInfo
{
    [Key]
    [DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }

    public string EmailAddress { get; set; }

}

public class EmailAccount
{
    [Key]
    [DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }
    ...
}

Now, if you execute a LINQ command like the following:

var recs = (from data in db.Persons
                            select data);
                foreach (var rec in recs)
                {
                    foreach (var email in rec.EmailAddressInfoList)
                    {
                        Console.WriteLine(email);
                    }
                }

You get the error:

Exception Details: System.InvalidOperationException: There is already an open DataReader associated with this Command which must be closed first.

To solve this, you need to tell EntityFramework/CodeFirst to include the EmailAddressInfoList in the query. All you need to do is change the db.Persons to db.Persons.Include("EmailAddressInfoList") as follows:

var recs = (from data in db.Persons.Include("EmailAddressInfoList")
            select data);

Then, it all works!

Hope this helps.