Using the repository pattern with Entity Framework (mvc storefront)

Question

Can anyone give a helping hand? I've been watching the videos for the MVC storefront and have created my own website using these techniques i.e. DDD, Repository pattern but I wish to use Entity Framework.

In the Interfaces it returns IQueryable but with Entity Framework should I return ObjectQuery instead? - I will be using LINQ.

Also in the storedfront example it goes something like this: IQueryable<Category> GetCategories();

Also in the MVC store the Category class was a built entity class (standard class) but with Entity Framework these classes are prebuilt in the object context - are they not?

So I should need to build them?

I am a little confused. If anyone has any helpful example or code it would be really helpful.

As I say, I have watched the videos from The MVC storefront using linq2sql but really would like to use Entity Framework.

Any ideas?

Thanks

Smithy

Cory House · Accepted Answer · 2011-04-30 17:09:12Z

9

Let me answer your questions one at a time:

Your repositories should return IQueryable<T>, not ObjectQuery. The reason is that the whole purpose of the repository pattern is to abstract away the specifics of your data store. This allows you to do things like substitute a mock repository when you unit test your controllers. If you make the repository return ObjectQuery, then you are not abstracting away the Entity Framework. Another way of saying this is the users of your repository should not know, as much as possible, that it is the Entity Framework which is doing the O/R mapping.

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edited Apr 30, 2011 at 17:09

Cory House

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answered Mar 30, 2009 at 13:14

Craig Stuntz

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segaco · Accepted Answer · 2009-03-30 01:14:57Z

6

Maybe if you see the Contact Manager Tutorial in the http://www.asp.net/learn/mvc/#MVC_SampleApp site, they use the Repository Pattern and the Entity Framework.

answered Mar 30, 2009 at 1:14

segaco

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Drevak · Accepted Answer · 2009-05-04 19:06:28Z

I started like you a few weeks ago, you will see it's pretty easy to work with EF. My project is small so i'm using the entities generated by the EF as my model classes, and you can add your own logic to them using a partial class.

Here's a simple method of one of my repositories, as a example:

    /// <summary>
    /// Finds a user by it's credentials
    /// </summary>
    /// <param name="oUser"></param>
    /// <returns></returns>
    public User FindByCredentials(string username, Byte[] password)
    {
        User user = null;

        if (!Validators.IsStringEmptyOrNull(username))
        {
            user = this.FindByCredentialsQuery(username, password).FirstOrDefault<User>();
        }

        return (Validators.IsNull(user)) ? new User() : user;

    }


    /// <summary>
    /// Finds a user by it's credentials
    /// </summary>
    /// <param name="username"></param>
    /// <param name="password"></param>
    /// <returns></returns>
    protected IQueryable<User> FindByCredentialsQuery(string username, Byte[] password)
    {
        var query = from Users in this.UserDataContext.Users
                    where
                        (Users.Username == username) &&
                        (Users.Password == password) &&
                        (Users.Enabled == true)
                    select Users;


        return query;
    }

Note that i'm using IQueryable only inside the repository, and return only the list of entities requested. This way i can control that the query to DB is always executed inside the Repo.

I was wondering about this myself. Returning IQueryable defers execution of the query, right? So the context and connection are hanging around?

tdykstra · Accepted Answer · 2011-05-11 16:37:23Z

3

A new MVC tutorial series includes an example of a repository that includes methods with parameters that let you specify filters, sortings, etc., without returning IQueryable: http://www.asp.net/entity-framework/tutorials/implementing-the-repository-and-unit-of-work-patterns-in-an-asp-net-mvc-application

answered May 11, 2011 at 16:37

tdykstra

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Comments

Søren · Accepted Answer · 2013-01-26 06:00:57Z

3

A nice generic repository for entity framework (active) : http://www.codeproject.com/KB/database/ImplRepositoryPatternEF.aspx

nowadays I use this one as Application Framework (a perfect repository included) http://efmvc.codeplex.com/

pls give it a shout ;)

edited Jan 26, 2013 at 6:00

answered Dec 1, 2010 at 7:21

Søren

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Gert Arnold · Accepted Answer · 2025-04-08 07:43:52Z

2

I'm not sure if that's correct, but I`m using L2E, translating generated objects to domain objects using AutoMapper 3rd party tool.

edited Apr 8 at 7:43

Gert Arnold

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answered May 4, 2009 at 18:32

Arnis Lapsa

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