How to structure Entityframework DB Contexts

Question

I haven't been able to find any answers online for this.

What are the advantages/disadvantages of using Multiple DB Contexts against using a single?
Is the below solution ok for setting related objects, (when saving to DB) (to make it more efficient, because I already have the ID, no need to fetch object)

I've heard its reccommened to use contexts like Using(MyContext c = MyContext) {}, at the moment I'm using the default MVC way, of having the context instantiated in the controller, is this ok?

  Person P = new Person(); 
  P.QuickSetCar(CarID); 
  db.People.Add(P); 
  db.saveChanges();

and

private void QuickSetCar(int CarID)
{
  if(this.Car == null) {
    Car C = new Car();
    C.ID = ID;
    this.Car = C;
 }
}

PinnyM · Accepted Answer · 2013-02-15 05:07:39Z

1

Using multiple contexts is always a disadvantage unless you have no choice (e.g. your data is dispersed across multiple databases).

Almost, but you can simplify your new car initialization to:

private void QuickSetCar(int CarID) {
  if(this.Car == null)
    this.Car = new Car(){ ID = CarID };
}

That's fine. Just don't use more than one context for the duration of the web transaction (request/response) and don't keep it around for longer than that either.

edited Feb 15, 2013 at 5:07

answered Feb 15, 2013 at 5:02

PinnyM

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Judo · Accepted Answer · 2013-02-15 07:03:24Z

1

Multiple contexts are normally only useful for very large models spread over multiple databases. If you are starting a project it is normally best to use a single context.
Your method for using IDs is fine.
Creating contexts within controllers is certainly workable but I would strongly suggest against it. This approach is often shown in demos and for basic scaffolding but in real world applications it is not a great idea. Large amounts of code will often be duplicated by instatiating and querying contexts in each controller. Also have a central repository will allow for much easier caching to improve performance.

answered Feb 15, 2013 at 7:03

Judo

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2 Comments

williamsandonz Over a year ago

Thanks!! Re: #3, my code is DRY, what do you mean by a central repository?

Judo Over a year ago

The repo is just a central location for all interactions with the context. It is hard for code to be DRY as the project grows if you are opening and querying contexts in each controller. A good starter for the repository pattern is at blog.appharbor.com/2012/10/31/…

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