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c#dependency-injectionrepository-patternunit-of-worksolid-principles
Zied R.
Zied R.

Reputation: 4964

UnitOfWork & Generic Repository, SOLID principles with Custom Repository

I'm using UnitOfWork and Repository patterns in my project. I'm trying to code clean.

This is my IUnitOfWork.cs (Application Layer)

public interface IUnitOfWork : IDisposable
{
    int Save();
    IGenericRepository<TEntity> Repository<TEntity>() where TEntity : class;
}

The implementation UnitOfWork.cs : (Persistence Layer)

public class UnitOfWork : IUnitOfWork
{      
    private readonly DBContext _context;
    private Hashtable _repositories;
    public UnitOfWork(DBContext context)
    {
        _context = context;
    }

    public IGenericRepository<T> Repository<T>() where T : class
    {
        if (_repositories == null)
            _repositories = new Hashtable();

        var type = typeof(T).Name;

        if (!_repositories.ContainsKey(type))
        {
            var repositoryType = typeof(GenericRepository<>);

            var repositoryInstance =
                Activator.CreateInstance(repositoryType
                    .MakeGenericType(typeof(T)), _context);

            _repositories.Add(type, repositoryInstance);
        }

        return (IGenericRepository<T>)_repositories[type];
    }

    public int Save()
    {
        // Save changes with the default options
        return _context.SaveChanges();
    }

    // etc.. Dispose()
}

My IGenericRepository.cs : (Application Layer)

public interface IGenericRepository<TEntity>
    where TEntity : class
{
    void Update(TEntity entity);
    void Delete(object id);
    void InsertList(IEnumerable<TEntity> entities);
    // etc..
}

In my service : (Application Layer)

var result = UnitOfWork.Repository<Entities.Example>().Delete(id);

And using Unity, I inject the dependency in the container.

  container.RegisterType<IUnitOfWork, UnitOfWork>(new HierarchicalLifetimeManager())

And it works like a charm.

Now I have a custom Repository ICustomRepository:

public interface ICustomRepository: IGenericRepository<Entities.Custom>
{
    void Test();
}

How can I access the Test() function using my IUnitOfWork? 

var result = UnitOfWork.Repository<Entities.Custom>().Test();  // not working

UPDATE:

@Thomas Cook give me a way using cast : 

   (UnitOfWork.Repository<Entities.Custom>() as ICustomRepository).Test();

I get a NullReferenceException:

System.NullReferenceException: 'Object reference not set to an instance of an object.'

Upvotes: 5

Views: 892

Answers (2)

Aage
Aage

Reputation: 6252

Whilst casting would work (if the repository wouldn't be null) you could ask yourself is this is useful; What good is an abstraction of you're going to depend on knowing its details, i.e.: the caller now knows it actually is a non-generic interface and type, namely a ICustomRepository (btw the reason you get the null ref probably is because UnitOfWork only creates the generic repositories and your custom repo doesn't exist).

A better (IMO) and more explicit way to design your Unit of Work not in a generic way but list all repositories:

public interface IUnitOfWork : IDisposable
{
    int Save();
    ICustomRepository CustomRepository {get;}
    IGenericRepository<Entities.Example> ExampleRepository {get;}
    // etc...
}

This way you don't need any casting or know its details.

Furthermore, I would recommend to pass all repositories to the constructor of the UnitOfWork from your dependency injection and don't make its responsibility too big.

public UnitOfWork(DBContext context, ICustomRepository customRepository ...)
    {
       //
    }

Just make sure you use the same instance of DbContext in your Unit of Work as the one that's injected into your repositories.

Upvotes: 1

Thomas Cook
Thomas Cook

Reputation: 4853

You'll have to cast, because UnitOfWork Repository method returns a IGenericRepository which doesn't declare Test. So you'll need to cast the returned value to a ICustomRepository which inherits IGenericRepository and bolts on the Test method.

Upvotes: 1

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