Best Practice of Repository and Unit of Work Pattern with Multiple DbContext

Question

I plan to develop a web application using ASP.NET MVC with Entity Framework 6 (Code First / POCO). I also want to use generic Repository and Unit of Work Pattern in my appli

Answer 1

I would suggest you to create UnitOfWork pattern with a Constructor parameter to accept DbContext -

public class UnitOfWork : IUnitOfWork
{
    private readonly IDbContext _context;

    private bool _disposed;
    private Hashtable _repositories;

    public UnitOfWork(IDbContext context)
    {
        _context = context;
    }

    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    public void Save()
    {
        _context.SaveChanges();
    }

    public virtual void Dispose(bool disposing)
    {
        if (!_disposed)
            if (disposing)
                _context.Dispose();

        _disposed = true;
    }

    public IRepository Repository() where TEntity : class
    {
        if (_repositories == null)
            _repositories = new Hashtable();

        var type = typeof(TEntity).Name;

        if (_repositories.ContainsKey(type)) return (IRepository) _repositories[type];

        var repositoryType = typeof (Repository<>);

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

        _repositories.Add(type, repositoryInstance);

        return (IRepository) _repositories[type];
    }
}

where IDbContext is -

public interface IDbContext
{
    IDbSet Set() where T : class;
    int SaveChanges();
    void Dispose();
}

And the repository implementation would be -

 public class Repository : IRepository where TEntity : class
    {
        internal IDbContext Context;
        internal IDbSet DbSet;

        public Repository(IDbContext context)
        {
            Context = context;
            DbSet = context.Set();
        }

        public virtual TEntity FindById(object id)
        {
            return DbSet.Find(id);
        }

        public virtual void Update(TEntity entity)
        {
            DbSet.Attach(entity);
        }
        public virtual void Delete(object id)
        {
            var entity = DbSet.Find(id);
            var objectState = entity as IObjectState;
            if (objectState != null)
                objectState.State = ObjectState.Deleted;
            Delete(entity);
        }

        public virtual void Delete(TEntity entity)
        {
            DbSet.Attach(entity);
            DbSet.Remove(entity);
        }

        public virtual void Insert(TEntity entity)
        {
            DbSet.Attach(entity);
        }

        public virtual List GetAll()
        {
            return DbSet.ToList();
        }
    }

With this approach you can create a UnitOfWork for individual DBContext and you have specific logic to commit or rollback in UnitOfWork.