ASP.NET 3.5 Extensions Preview

Re: Entity Framework - Detached objects

cgeers — Tue, 19 May 2009 09:20:57 GMT

ruben0,

Using a single instance for your context (= singleton) is not the best approach for an ASP.NET application because as you've said each user will wind up using that instance. Using a singleton context would work better in a WinForms application.

Instantiating a new object for each "controller" class is a workable approach, but it not necessary either. A better approach would be to use a context per Http Request.

I wrote a blog post about this a while back:

http://cgeers.wordpress.com/2009/02/21/entity-framework-objectcontext/

You could then pass in this context instance to the constructor of your controller classes. You could opt to use dependency injection for this...

The following code is provided for illustrative purposes:

1    public class MyController: IController
2    {
3      private IObjectContextProvider provider;
4    
5      public MyController(IObjectContextProvider provider)
6      {
7        this.provider = provider;
8      }
9    
10     public void SomeMethod()
11     {
12       MyContext context = provider.GetContext();
13       // ...
14     }
15   }

Regards,

 Christophe

Re: Entity Framework - Detached objects

MisterFantastic — Tue, 21 Apr 2009 07:13:09 GMT

Hi,

You can use a single context itself. Noneed of using two context for two controller. That will solve the problem.

Please let me know if you have problems.

Thanks,

Thani

Re: Entity Framework - Detached objects

puruforum — Tue, 24 Mar 2009 09:35:36 GMT

Hi,

Please explain more about it.

if you are using singleton and doing check with user ==null then another part of the code needed otherwise make user to null after savechanges.

and other solution is at the time of creation every time create new user.

Thanks,

Puru

Entity Framework - Detached objects

ruben0 — Thu, 19 Mar 2009 15:19:18 GMT

First I was using a singleton class with only one instance of my entities (my context) but that means every user on the site uses that same instance, so I changed it to use a new instance per controller.

I've got my "UserController" and "CompanyController" (both used to update or get users/companies)

A User object has a link to Company.

What I do in my usercontroller:

1    public void addUser(UserDTO userDTO) {
2      User user = User.CreateUser(0, .....)
3      user.Company = new CompanyController().getCompany(userDTO.Company.companyId);
4      context.AddToUsers(user);
5      context.SaveChanges();
6    }

The problem I had here was the "Company" object was from another context (made in the companycontroller), so I thought, I'd just detach the Company object in CompanyController before I return it, so the "AddToUsers()" attaches it again.

Is there a way to make this "AddToUsers" attach this? I can solve my problem by using this code:

1    Company c = new Companycontroller().getCompany(userDTO.Company.companyId);
2    context.AttachTo("Companies", c);
3    user.Company = c;

But I'd prefer a way it's done automatically, because I have a lot more objects and having to hardcode all these attachments will give a lot of messy code..