How-to inject the Entity Framework DbContext into the ConfigurationBasedRepository of SharpRepository

Question

I really would like to use SharpRepository together with Ninject, but I do not understand how to configure Ninject to share the Entity Framework DbContext between the repositories.

I am using Entity Framework version 5 and Ninject version 3.

Currently I am using Ef5Repository in my source code, but I want to replace it with ConfigurationBasedRepository. But I cannot figure out how to pass (or inject) the EF DbContext to the repositories.

Example (current state):

using SharpRepository.Repository;

public interface IProductRepository : IRepository<Product>
{
}

using SharpRepository.Ef5Repository;
using System.Data.Entity;

// TODO Tightly coupled to Ef5Repository.
public class ProductRepository : Ef5Repository<Product>, IProductRepository
{
    // TODO The DbContext has to be injected manually.
    public ProductRepository(DbContext context) : base(context)
    {
    }

    // [...]
}

Goal:

using SharpRepository.Repository;

public interface IProductRepository : IRepository<Product>
{
}

public class ProductRepository : ConfigurationBasedRepository<Product, int>, IProductRepository
{
    // [...]
}

I've already read the two blog posts SharpRepository: Getting Started and SharpRepository: Configuration, but they both do not help me, since:

1. The used DIC is StructureMap, not Ninject.
2. The source code examples are incomplete (e.g. usage of not declared variables).

So my question: Can someone provide me with some source code example how-to to achieve the goal described above (sharing one Entity Framework DbContext instance between all repositories extending ConfigurationBasedRepository)?

Answer 1

First, you will need to install the SharpRepository.Ioc.Ninject NuGet package. There are extension methods in here for hooking up Ninject to handle the loading a generic repository and setting the dependency resolver that SharpRepository uses.

Where ever you are setting up your Ninject binding rules (all the calls to kernel.Bind<>), you will need to add:

kernel.BindSharpRepository();

Next, in your Global.asax, or App_Start code, or your Bootstrapper logic (where ever you are calling application startup code) you will need to add the following:

// kernel is the specific kernel that you are setting up all the binding for
RepositoryDependencyResolver.SetDependencyResolver(new NinjectDependencyResolver(kernel));

This will tell SharpRepository to use this Ninject Kernel when getting a new DbContext.

The last thing to do is to setup the rules for binding for the DbContext itself. If you are in a web application you will most likely want the scope of the DbContext to be per request. I personally don't use Ninject but I found this reference for using InRequestScope. I believe your code would look something like this:

kernel.Bind<DbContext>().To<MyCustomEfContext>().InRequestScope().WithConstructorArgument("connectionString", ConfigurationManager.ConnectionStrings["MyCustomEfContext"].ConnectionString);

Most people won't need this next piece but if you have custom logic in your CustomEfContext (I have an override for logging on calls to SaveChanges() for example), then you'll need to define your custom context type in the configuration file like so:

<repositories>
  <repository name="ef5Repository" connectionString="CustomEfContext" cachingStrategy="standardCachingStrategy" dbContextType="My.Data.CustomEfContext, My.Data" factory="SharpRepository.Ef5Repository.Ef5ConfigRepositoryFactory, SharpRepository.Ef5Repository" />
</repositories>

Where dbContextType defines the type of the custom DbContext you are using using the full type, namespace syntax. If you do this then you'll need to set Ninject to Bind on the custom context by changing .Bind<DbContext>() to .Bind<CustomEfContext>(). But like I said normally you can use DbContext directly without an issue.