How should you use UnitofWork pattern on my asp.net-mvc site (using nhibernate and ninject)

Question

i have followed the pattern on this site to hook up ninject and nhibernate to my asp.net-mvc3 site.

Here is the code in my global.aspx.cs:

 internal class ServiceModule : NinjectModule
{
    public override void Load()
    {
        var helper = new NHibernateHelper(connectionString);
        Bind<ISessionFactory>().ToConstant(helper.SessionFactory)
            .InSingletonScope();

        Bind<IUnitOfWork>().To<UnitOfWork>()
            .InRequestScope();
        Bind<ISession>().ToProvider(new SessionProvider())
            .InRequestScope();
        Bind<IIntKeyedRepository<FAQ>>().To<Repository<FAQ>>()
            .InRequestScope();
       }

the issue is that i now need to do Update() and Add() in my controllers;

I have this as my controller code:

    public FAQController(IIntKeyedRepository<FAQ> faqRepository, IUnitOfWork unitOfWork)
    {
        _faqRepository = faqRepository;
        _unitOfWork = unitOfWork;
    }


  [Authorize]
    [AcceptVerbs(HttpVerbs.Post)]
    [ValidateInput(false)]
    public ActionResult AddFAQ(FAQ contact)
    {
        var c = new FAQ {Question = contact.Question, Answer = contact.Answer};
        _faqRepository.Add(c);
        _unitOfWork.Commit();
        return RedirectToAction("Index");
    }

my main question is that it feels wrong to pass in Iunitofwork in the constructor as many other actions don't need it. I only really need it for the actions where i do updates and inserts into my db. Since i am using ninject IOC on the link above it seems to say to pass this unitofwork object through IOC.

So, is there a better more optimized way to using the UnitOfWork pattern with IOC in asp.net-mvc that does call beingtransaction for every method in my controller.

Answer 1

An alternative way to handle transactions is to use an IActionFilter Open the transaction in OnActionExecuting and commit on OnActionExecuted

public class TransactionFilter : IActionFilter
{
    private readonly ISession session;
    private ITransaction transaction;

    public TransactionFilter(ISession session)
    {
        this.session = session;
    }

    public void OnActionExecuting(ActionExecutingContext filterContext)
    {
        this.transaction = this.session.BeginTransaction();
    }

    public void OnActionExecuted(ActionExecutedContext filterContext)
    {
        try
        {
            if (this.transaction.IsActive)
            {
                if (filterContext.Exception == null)
                {
                    this.transaction.Commit();
                }
                else
                {
                    this.transaction.Rollback();
                }
            }
        }
        finally
        {
            this.transaction.Dispose();
        }
    }
}

Define an attribute to mark the actions that use a transaction:

[AttributeUsage(AttributeTargets.Method)]
public class TransactionAttribute : Attribute
{ 
}

Change your Ninject configuration:

internal class ServiceModule : NinjectModule
{
    public override void Load()
    {
        var helper = new NHibernateHelper(connectionString);
        Bind<ISessionFactory>().ToConstant(helper.SessionFactory)
            .InSingletonScope();

        Bind<ISession>().ToProvider<SessionProvider>().InRequestScope();
        Bind(typeof(IRepository<>)).To(typeof(Repository<>));
        Bind(typeof(IIntKeyedRepository<>)).To(typeof(Repository<>));
        BindFilter<TransactionFilter>(FilterScope.Action, null)
            .WhenActionMethodHas<TransactionAttribute>();
    }
}

Finally change your controller:

public FAQController(IIntKeyedRepository<FAQ> faqRepository)
{
    _faqRepository = faqRepository;
}


[Transaction]
[Authorize]
[AcceptVerbs(HttpVerbs.Post)]
[ValidateInput(false)]
public ActionResult AddFAQ(FAQ contact)
{
    var c = new FAQ {Question = contact.Question, Answer = contact.Answer};
    _faqRepository.Add(c);
    return RedirectToAction("Index");
}