ASP DBContext Best Practies

在谷歌搜索了一段时间后，我想知道DBContext（EntityFramework或Linq-to-Sql）的最佳实践方法。

在实践中，我会撒谎知道以下"模式"中的哪一种缺点较少：

1） 从这里获取代码

public class ContextFactory
{
    [ThreadStatic]
    private static DBDataContext context;
     //Get connectionString from web.config
    private static readonly string connString = ConfigurationManager.ConnectionStrings["ConnectionString1"].ConnectionString; 
    public static DBDataContext Context()
    {
        if (context == null)
            context = new DBDataContext(connString);
        return context;
    }
    public static void FlushContext()
    {
        context = new DBSkillDataContext(connString);
    } 
} 

这样，每次初始化控制器时，我都会使用 FlushContext。

2）以这种方式（从这里获取代码）

public class UnitOfWork : IUnitOfWork, IDisposable
   {
    DBContext context= null;
    IUserRepository userRepo = null;
    IAccountRepository accountRepo = null; 
    public UnitOfWork()
    {
        context= new DBContext();
        userRepo= new UserRepository(context);
        accountRepo= new accountRepo(context); 
    }
    public IUserRepository userRepo 
    {
        get
        {
            return userRepo;
        }
    }
    public IAccountRepository accountRepo 
    {
        get
        {
            return accountRepo;
        }
    } 
    public void Dispose()
    {
        // If this function is being called the user wants to release the
        // resources. lets call the Dispose which will do this for us.
        Dispose(true);
        // Now since we have done the cleanup already there is nothing left
        // for the Finalizer to do. So lets tell the GC not to call it later.
        GC.SuppressFinalize(this);
    }
    protected virtual void Dispose(bool disposing)
    {
        if (disposing == true)
        {
            //someone want the deterministic release of all resources
            //Let us release all the managed resources
            context= null;
        }
    }
    ~UnitOfWork()
    {
        // The object went out of scope and finalized is called
        // Lets call dispose in to release unmanaged resources 
        // the managed resources will anyways be released when GC 
        // runs the next time.
        Dispose(false);
    }
} 
public abstract class AController : Controller
{
    private IUnitOfWork IUnitOfWork;
    protected IUnitOfWork UnitOfWork_
    {
        get { return IUnitOfWork; }
    }
    public AController(IUnitOfWork uow)
    {
        this.IUnitOfWork = uow; 
    }
}
public class UserController : AController
{
    // use our DbContext unit of work in case the page runs
    public UserController()
        : this(new UnitOfWork())
    {
    }
    // We will directly call this from the test projects
    public UserController(UnitOfWork unitOfWork)
        : base (unitOfWork)
    {
    }
    public ActionResult Index()
    {
        List<User> users= UnitOfWork_.usersRepo.GetUsers();
        return View(users);
    }

}

所以我要问的是，以上哪一个是最佳实践？