entity framework programming against interface and repository pattern - asp.net-mvc-3

Question

I am developing in ASP.NET MVC3 and EntityFramework.
I want my model to follow an interface :
public class Account : IAccount
{
public string Id { get; set; }
public DateTime Date { get; set; }
public string Language { get; set; }
}
public interface IAccount
{
string Id { get; set; }
DateTime Date { get; set; }
string Language { get; set; }
}
Here's my Context
public class EFContext : DbContext, IContext
{
public DbSet<Account> Accounts { get; set; }
}
And here's the repository :
public interface IRepository<T> where T : class
{
IQueryable<T> All { get; }
int Count { get; }
bool Contains(Expression<Func<T, bool>> predicate);
void Create(T item);
void Update(T item);
void Delete(Expression<Func<T, bool>> predicate);
void Delete(T item);
}
public class EFRepository<T> : IRepository<T> where T : class
{
private EFContext _context;
public EFRepository(IUnitOfWork uow)
{
this._context = (EFContext)uow.Context;
}
protected DbSet<T> DbSet
{
get
{
return _context.Set<T>();
}
}
public IQueryable<T> All
{
get
{
return DbSet.AsQueryable();
}
}
public virtual int Count
{
get
{
return DbSet.Count();
}
}
public bool Contains(Expression<Func<T, bool>> predicate)
{
return DbSet.Count(predicate) > 0;
}
public virtual void Create(T item)
{
DbSet.Add(item);
}
public virtual void Update(T TObject)
{
var item = DbSet.Attach(TObject);
_context.SetItemState(TObject, EntityState.Modified);
}
public virtual void Delete(Expression<Func<T, bool>> predicate)
{
var objects = DbSet.Where(predicate);
foreach (var obj in objects)
{
DbSet.Remove(obj);
}
}
public virtual void Delete(T TObject)
{
DbSet.Remove(TObject);
}
}
Now, I want to use IRepository<IAccount> but this will ask the context for DbSet<IAccount>. This leads to an error since the Context contains a DbSet<Account>.
I then tried the solution proposed here for Linq2Sql : http://iridescence.no/post/Linq-to-Sql-Programming-Against-an-Interface-and-the-Repository-Pattern.aspx
So I added this function to my EFContext
public new DbSet<T> Set<T>() where T : class
{
var ciccio = TableMaps[typeof(T)];
return (DbSet<T>)base.Set(ciccio).Cast<T>();
}
But it doesn't work.
Do anyone have a suggestion?
Thx

Answer 1

What benefit are you receiving from using an interface for your entities? I don't see any value here. Typically, you use Interfaces to remove dependencies upon the implementation, but that's not what you're achieving here because you're returning a concrete DbSet of objects.
Your entities are already Poco's. They don't have dependencies on other implemntations, and they have no code in them other than a getter/setter. Using an interface is redundant and pointless.

Answer 2

I've found a workaround. I kind of like it so I want to share it.
I rewritten my EFRepository :
public class EFRepository<T, W> :
IRepository<T> where T : class
where W : class, T
{
private EFContext _context;
public EFRepository(IUnitOfWork uow)
{
this._context = (EFContext)uow.Context;
}
protected DbSet<W> DbSet
{
get
{
return _context.Set<W>();
}
}
public IQueryable<T> All
{
get
{
return DbSet.AsQueryable<T>();
}
}
public virtual int Count
{
get
{
return DbSet.Count();
}
}
public bool Contains(Expression<Func<T, bool>> predicate)
{
return All.Count(predicate) > 0;
}
public virtual void Create(T item)
{
DbSet.Add(item as W);
}
public virtual void Update(T TObject)
{
var item = DbSet.Attach(TObject as W);
_context.SetItemState(TObject, EntityState.Modified);
}
public virtual void Delete(Expression<Func<T, bool>> predicate)
{
var objects = All.Where(predicate);
foreach (var obj in objects)
{
DbSet.Remove(obj as W);
}
}
public virtual void Delete(T TObject)
{
DbSet.Remove(TObject as W);
}
}
So now basically all I need to do now is
IRepository<IAccount>> accRepository = new EFRepository<IAccount, Account>(uow);
I am happy with this solution, but still I'm not sure it is the best one, so any comments will be appreciated.
Thanks