should a repository be injected through a constructor or wrapped in a using?

Question

When using entity framework, is it bad practice to inject the repository into a controller?

For example if I have a service:

public class DogService
{
    IMyDbContext _myDbContext;
    public DogService(IMyDbContext myDbContext)
    {
        _myDbContext = myDbContext;
    } 


    public void CreateDog(string name)
    {
        //create a dog using the myDbContext
    }
}

Would the above be bad practice since we are not explicitly disposing of the repository, and would it be better to do:

public void CreateDog(string name, IMyDbContext myDbContext)
{
     using(myDbContext)
     {
          //create a dog using the myDbContext
     }
}

the stucture of mydbcontext:

public class MyDbContext : DbContext, IMyDbContext {}

How do I dispose of the myDbContext?

You don't typically "inject" a context. A context is created, used, and destroyed. More commonly, a _repository_ or something else is injected that then _uses_ the context. — D Stanley, Sep 26 '16 at 18:19
To answer the other question, whatever _creates_ the disposable object is typically responsible for _disposing_ of it. When you inject it into another class it complicates things. — D Stanley, Sep 26 '16 at 18:22
@DStanley does that mean that my connection is disposed of as long as the object that creates the repository is disposed? — Alex Gordon, Sep 26 '16 at 18:24
Only if the object that creates it disposes of it in the `Dispose` method. — D Stanley, Sep 26 '16 at 18:43
You could use a factory to create the context and then wrap the factory call in a `using` if you don't want your DI framework to handle this for you. — stephen.vakil, Sep 26 '16 at 18:49
you could also pass the context in as a factory such as Func... though you could just make your repository IDisposable and handle its lifetime from your IOC container. — Matthew Whited, Sep 26 '16 at 19:49
_How_ do you inject it? Because that is where the answer will come from. — H H, Sep 26 '16 at 21:06

score 2 · Answer 1 · edited May 23 '17 at 12:15

2

Main question - Will it be a good idea to inject the DBcontext using Dependency Injection, if Yes, then how does it get disposed

Yes it can be injected, if using Ninject IOC, following would help:

kernel.Bind<DBContext>().ToSelf().InRequestScope();

check out the following link, it describes both the patterns and also provides details regarding how to create a single DBcontext per HttpRequest, no matter how many controllers get invoked in the process.

Another useful link, How to handle DBContext when using Ninject

edited May 23 '17 at 12:15

Community

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answered Sep 26 '16 at 18:47

Mrinal Kamboj

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Not only with Ninject of course. Lifetime management becomes the responsibility of the DI container. – H H Sep 26 '16 at 21:05
@HenkHolterman agreed Ideally that shall be the case but with so many DI frameworks floating around, I am little vary of a blanket claim, Popular one like Ninject I have used, so is 100 % sure – Mrinal Kamboj Sep 28 '16 at 05:22

Sampath · Answer 2 · 2016-09-26T19:14:05.350

Yes, you can inject the repository interface when you use the repository pattern. I mean you can inject it using controller's constructor.

Lifetime of a Repository :

All repository instances are Transient. It means, they are instantiated per usage.Hence you don't need to worry about the dispose of the Context.

Here is an example : this is a repository pattern.you have to inject the Interface of the repository.On this example where it uses a service layer.But you can do it on your controller as well.

public class PersonAppService : IPersonAppService
{
    private readonly IRepository<Person> _personRepository;

    public PersonAppService(IRepository<Person> personRepository)
    {
        _personRepository = personRepository;
    }

    public void CreatePerson(CreatePersonInput input)
    {        
        person = new Person { Name = input.Name, EmailAddress = input.EmailAddress };
        _personRepository.Insert(person);
    }
}

You can read more about it here : Repositories

Please don't use `inline code` to highlight random programming-related terms. It doesn't make your posts more readable, on the contrary even. See also [When should code formatting be used for non-code text?](http://meta.stackoverflow.com/questions/254990/when-should-code-formatting-be-used-for-non-code-text). — CodeCaster, Sep 26 '16 at 18:55
@CodeCaster OK sure, Thanks.I think this is the 2nd time where you have given this advice.I'll follow it here after :) — Sampath, Sep 26 '16 at 18:57

score -3 · Answer 3 · answered Sep 26 '16 at 18:42

-3

You could let DogService implement IDisposable and call myDbContext.Dispose() from DogService's Dispose method.

answered Sep 26 '16 at 18:42

user1796440

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Who will call that Dispose ? – Mrinal Kamboj Sep 26 '16 at 18:44
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@MrinalKamboj it would be called by creating an instance of DogService within a using block: – user1796440 Sep 26 '16 at 18:45
1

You have not understood the Dependency Injection and its working in that case, if feasible, OP would have done this long back – Mrinal Kamboj Sep 26 '16 at 18:48

should a repository be injected through a constructor or wrapped in a using?

3 Answers3