How to avoid repositories that duplicate code - asp.net-mvc

Question

I have successfully setup a simple mvc application that lists teams. I'm using Ninject to inject the appropriate repository depending on the controller (thanks to stack overflow ;). All looks good, except that the repository code looks exactly the same. And I know that's wrong. So my TeamRepository has two classes (for now).
public class SwimTeamRepository : ITeamRepository<SwimTeam>
{
private readonly Table<SwimTeam> _teamTable;
public SwimTeamRepository(string connectionString)
{
_teamTable = (new DataContext(connectionString).GetTable<SwimTeam>());
}
public IQueryable<SwimTeam> Team
{
get { return _teamTable; }
}
}
public class SoccerTeamRepository : ITeamRepository<SoccerTeam>
{
private readonly Table<SoccerTeam> _teamTable;
public SoccerTeamRepository(string connectionString)
{
_teamTable = (new DataContext(connectionString).GetTable<SoccerTeam>());
}
public IQueryable<SoccerTeam> Team
{
get { return _teamTable; }
}
}
They look exactly the same except for the Class and Table name, so clearly I need to re-factor this. What would be the best approach here? Singleton? Factory Method?
Thanks in advance!

Answer 1

You could use generics:
public interface ITeamRepository<T>
{
}
public class TeamRepository<TTeam> : ITeamRepository<TTeam>
where TTeam : Team
{
private readonly Table<TTeam> _teamTable;
public TeamRepository(string connectionString)
{
_teamTable = (new DataContext(connectionString).GetTable<TTeam>());
}
public IQueryable<TTeam> Team
{
get { return _teamTable; }
}
}
public class Team
{
}
public class SwimTeam : Team
{
}
Then use it like so...
public void MyMethod()
{
var repository = new TeamRepository<SwimTeam>();
}
...and set up your IoC container w/ Ninject like so...
public class MyModule : NinjectModule
{
public override void Load()
{
Bind<ITeamRepository<SwimTeam>>
.To<TeamRepository<SwimTeam>>();
}
}
public void MyMethod()
{
var repository = kernel.Get<ITeamRepository<SwimTeam>>();
}
If you want to get REAL generic and have a single repository for ALL of your mapped classes, you can do something like this:
public interface IRepository
{
IQueryable<T> Get<T>() where T : class, new();
}
public class Repository : IRepository, IDisposable
{
private DataContext _dataContext;
public Repository(string connectionString)
{
_dataContext = new DataContext(connectionString);
}
public IQueryable<T> Get<T>()
where T : class, new()
{
return _dataContext.GetTable<T>().AsQueryable();
}
public void Dispose()
{
if (_dataContext != null)
{
_dataContext.Dispose();
_dataContext = null;
}
}
}
...which you could call like so (after setting up your Ninject container)...
using (var repository = kernel.Get<IRepository>())
{
var swimTeam = repository.Get<SwimTeam>();
}
Since Ninject takes care of the life-cycle management of your objects, you don't HAVE to wrap the repository in a using statement. In fact, you don't want to use a using statement there at all if you plan to use the repository more than once within the scope of its lifetime. Ninject will automatically dispose of it when it's life-cycle ends.
Here's a good article by Rob Conery on using this kind of technique to reduce the friction of using different ORMs.
EDIT by keeg:
I Think
public class TeamRepository<TTeam> : ITeamRepository<TTeam> where TTeam : Team {}
Should be
public class TeamRepository<TTeam> : ITeamRepository<TTeam> where TTeam : class {}
Please correct if I'm wrong.

Answer 2

Is this what you want?
public class TeamRepository : ITeamRepository<T>
{
private readonly Table<T> _teamTable;
public TeamRepository(string connectionString)
{
_teamTable = (new DataContext(connectionString).GetTable<T>());
}
public IQueryable<T> Team
{
get { return _teamTable; }
}
}