UnitOfWork & Generic Repository, SOLID principles with Custom Repository

Question

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.'

Answer 1

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.