Using statements for DBContext in MVC

Question

I'm using ASP.NET MVC 4.5 with Entity Framework and everything I'm reading says my database context should be enclosed in a using statement to prevent memory leaks. However, when I pass my model to my view I lose the ability to join to other tables.

So if I have a model that has:

public class people
{
   public int id { get; set; }
   public sting name { get; set; }
   public virtual stuff things { get; set; }
}
public class stuff
{
   public int id { get; set; }
   public string name { get; set; }
   public int thingType { get; set; }
}

But if in my view I want to to loop add grab all of a persons's stuff I can't if I created my context in a using statement. What's the correct way to handle this?

Joe Enos · Accepted Answer · 2013-06-27 15:35:35Z

3

You can retrieve the children while the context is still open. You can do it eagerly or lazily:

using (var context = new SomeContext()) {
    // This will do a JOIN on the SQL query,
    // which will bring everything in at once.
    var thePerson = context.people.Include("things").Single(p => p.id == 4);
}

using (var context = new SomeContext()) {
    // This will fire two queries but will retrieve
    // the same data as the previous example
    var thePerson = context.people.Single(p => p.id == 4);
    var theStuff = thePerson.things.ToList();
}

edited Jun 27, 2013 at 15:35

answered Jun 27, 2013 at 15:28

Joe Enos

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1 Comment

DR913 Over a year ago

Fantastic. This is exactly what I was missing. Thanks for the help!

SLaks · Accepted Answer · 2013-06-27 15:45:32Z

0

You should call ToList() on the child collections when setting the ViewModel inside the using block to fetch the child relations before disposing the context.

edited Jun 27, 2013 at 15:45

answered Jun 27, 2013 at 15:08

SLaks

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3 Comments

Joe Enos Over a year ago

I don't think ToList() will fetch the children automatically - wouldn't you have to explicitly ask for them either eagerly with an .Include(), or lazily by calling the property while the context is still alive? I could be wrong with code first, but with database-first, you only get what you ask for.

Steve0 Over a year ago

I also am confident that ToList() will not fetch the child relations alone. They need to be explicitly retrieved before the context is disposed.

SLaks Over a year ago

@Steve: I meant on the child collection. Clarified.

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