What is the best approach to set up an entity framework context?

c# entity-framework

Question

When initialize an entity framework context.

One is to initialize at class level, such as

public class EntityContactManagerRepository
    : ContactManager.Models.IContactManagerRepository
{
    private ContactManagerDBEntities _entities = new ContactManagerDBEntities();

    // Contact methods
    public Contact GetContact(int id)
    {
        return (from c in _entities.ContactSet.Include("Group")
                where c.Id == id
                select c).FirstOrDefault();
    }
}

The other way is to initialize at the method level.

public class EntityContactManagerRepository
    : ContactManager.Models.IContactManagerRepository
{    
    // Contact methods
    public Contact GetContact(int id)
    {
       using (var entities = new ContactManagerDBEntities())
           return (from c in entities.ContactSet.Include("Group")
               where c.Id == id
               select c).FirstOrDefault();
    }
}

From an Ado.Net background, I prefer the later one-initialize in method, but the first one is from the example developed by Stephen Walthe. Or another question, does it matter at all?

1
37
2/4/2011 1:07:20 AM

Accepted Answer

It does matter, because the context controls the lifetime of change tracking data, and also impacts which object instances you can link together when you edit the objects, since objects on two different contexts cannot have a relationship with each other. It looks to me like the examples you're sharing come from an ASP.NET MVC application. In this case, I generally use one entity context per request, since requests are short-lived, and since it's common, when updating an object in a request, to have to fetch other objects and create relationships between them.

On the other hand, you don't want to keep an entity context around for a long time, because it will chew up memory as it tracks changes to more and more objects.

This may seem like an argument for the "one context per class" option, but it isn't, really. It's more like an argument for "one context per unit of work."

31
6/30/2009 2:12:25 PM

Popular Answer

Generally speaking: it's context per request in ASP.NET and context per window in WinForms/WPF.

There's an article that explains quite well the reasoning behind the context per request paradigm: Entity Framework Object Context Scope



Related Questions





Related

Licensed under: CC-BY-SA with attribution
Not affiliated with Stack Overflow
Licensed under: CC-BY-SA with attribution
Not affiliated with Stack Overflow