Question

I’m using ASP.NET MVC with Castle Windsor as my IoC container with the component lifestyle set to PerWebRequest. My repository (which is the dependency that’s injected) creates an instance of Entity Framework’s ObjectContext in the constructor and I store that in a private instance variable. My repository implements IDisposable and inside my Dispose method, I dispose the ObjectContext. I think all of this is pretty standard and here’s a simplified illustration:

Repository:

 public class Repository : IRepository {

    private MyContext _dc; // MyContext inherits from ObjectContext

    public Repository() {
        _dc = new MyContext();
    }

    public void Dispose() {;
        _dc.Dispose();
    }
}

To ensure that there’s no memory leak and that my Repository’s Dispose() is called, I override DefaultControllerFactory’s ReleaseController method to release Windsor’s container:

public class WindsorControllerFactory : DefaultControllerFactory {
        IWindsorContainer _container;

        public WindsorControllerFactory(IWindsorContainer container) {
            _container = container;
            // Do stuff to register all controller types
        }

        protected override IController GetControllerInstance(RequestContext requestContext, Type controllerType) {
            // Do stuff to resolve dependency
        }

        public override void ReleaseController(IController controller) {
            // by releasing the container, Windsor will call my Dispose() method on my repository
            _container.Release(controller);
            base.ReleaseController(controller);
        }
    }

I think all of this is pretty standard. However, I’d like to spin off a parallel thread, and inside that parallel thread utilize the IRepository dependency. My problem is that my repository will have already been disposed by the time I use it:

public class HomeController : Controller {

    IRepository _repository;

    public HomeController(IRepository repository) {
        _repository = repository;
    }

    public ActionResult Index() {
        var c = _repository.GetCompany(34);

        new Task(() => {
            System.Threading.Thread.Sleep(2000); // simulate long running task
            // will throw an error because my repository (and therefore, ObjectContext) will have been disposed.
            var c2 = _repository.GetCompany(35);
        }).Start();

        return Content(c.Name, "text/plain");
    }
}

How do other people solve this problem? How do you pass your dependencies to a parallel thread?

Thanks in advance.

Answer 1

Create a new Repository instance. ObjectContexts are inexpensive to construct.

OR, you could attach the responsibility of disposing the Repository to the long running thread. I messed around with it, I think these alterations to your code will solve your problem:

In your WindsorControllerFactory

    protected override IController GetControllerInstance(RequestContext requestContext, Type controllerType)
    {
        IController controller;
        // Do stuff to resolve dependency
        if(controller is LongTaskController)
        {
            ((LongTaskController) controller).CompleteLongTask += (sender, args) => _container.Release(controller);
        }
    }

    public override void ReleaseController(IController controller)
    {
        // by releasing the container, Windsor will call my Dispose() method on my repository
        if(!(controller is LongTaskController && ((LongTaskController)controller).HasLongTask)
        {
            _container.Release(controller);
        }
        base.ReleaseController(controller);
    }

In HomeController

public class HomeController : LongTaskController
{
    private readonly IRepository _repository;
    public HomeController(IRepository repository)
    {
        _repository = repository;
    }
    public ActionResult Index()
    {
        var c = _repository.GetCompany(34);
        DoLongTask(() =>
        {
            Thread.Sleep(200);
            var c2 = _repository.GetCompany(35);
        });
        return Content(c.Name, "text/plain");
    }
}

And the new base controller

public abstract class LongTaskController: Controller,IHasLongTask
{
    private bool _hasLongTask;
    public bool HasLongTask { get { return _hasLongTask; } }
    public event EventHandler CompleteLongTask;
    void IHasLongTask.DoLongTask(Action action) { DoLongTask(action); }
    protected void DoLongTask(Action action)
    {
        _hasLongTask = true;
        if (CompleteLongTask == null)
        {
            throw new NullReferenceException("Controller.CompleteLongTask cannot be null when Controller does a long running task.");
            action += () => CompleteLongTask(this, EventArgs.Empty);
        }
        new Task(action).Start();
    }
}
public interface IHasLongTask
{
    bool HasLongTask { get; }
    void DoLongTask(Action action);
    event EventHandler CompleteLongTask;
}