Autofac Webform Integration: Manual Property Injection

Question

Consider this autofac registration module for a webform MVP style application, where I register a couple of components by providing some parameters dependency.

public class SampleModule : Module
{
    protected override void Load(ContainerBuilder builder)
    {
        builder.RegisterType<FooService>().As<IFooService>();
        builder.Register<FooPresenter>((c, p) => 
                            new FooPresenter(p.Named<IFooView>("view"),
                                             c.Resolve<IFooService>(p),
                                             p.Named<string>("connectionString")))
                                             .InstancePerHttpRequest();
        base.Load(builder);
    }
}

In the page I can resolve the type using some code like this:

protected override void OnPreInit(EventArgs e)
{
    base.OnPreInit(e);
    var cpa = (IContainerProviderAccessor) HttpContext.Current.ApplicationInstance;
    var cp = cpa.ContainerProvider;

    // Resolve presenter
    var presenter = cp.RequestLifetime.Resolve<FooPresenter>(
                new NamedParameter[] 
                {
                    new NamedParameter("connectionString", "xyz"), 
                    new NamedParameter("view", this)
                });
}

But I would really like to use property injection and manage the dependency on the parameters at that level; Something like this for example:

public FooPresenter Presenter { get; set; }

protected override void OnPreInit(EventArgs e)
{
    base.OnPreInit(e);
    var cpa = (IContainerProviderAccessor) HttpContext.Current.ApplicationInstance;
    var cp = cpa.ContainerProvider;

    // Parameters bindings?
    cp.RequestLifetime.InjectProperties(this);
}

Is there something that I can leverage on Autofac? Thanks in advance.

score 2 · Accepted Answer · edited May 23 '17 at 09:59

2

Yes, there is ASP.NET integration which will inject page-level properties.

See the "Add Modules to Web.config" section here:

http://code.google.com/p/autofac/wiki/AspNetIntegration

Edit: Sorry for misunderstanding the question. I see now that you are not asking if property injection is available, but rather how to use it in conjunction with named parameters.

I am going to make an inference and say the reason you need named parameters is solely to pass the view to the presenter. The connection string shouldn't really be the page's responsibility; you can probably make that a property on SampleModule and read it from there.

I have a preferred approach to MVP/Autofac which has been battle-tested for years. It is clean, provides some nice extension points, and keep pages relatively free of implementation details. You can find the overview in my answer to this question:

Injecting Lower Layer Dependency in Presenter in an ASP.NET MVP Application

edited May 23 '17 at 09:59

Community

1
1

answered Sep 28 '11 at 14:55

Bryan Watts

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Sorry for not being too clear with my question. The problem I'm trying to solve here is how to bind the named parameters when using the property injection feature of autofac. – Fab60 Sep 28 '11 at 15:16
Thanks Bryan, I appreciated your clever solution for the presenter/view linkage. You are right that the connection parameter is in fact a spurious dependency of the presenter (the legacy part of the application is storing this in the Application object). Anyway, I think it should be beneficial having in Autofac a way to bind parameters in the property injection scenario; just like the Resolve method actually does by having an IEnumerable on its overloads. – Fab60 Oct 06 '11 at 13:05
I understand. Because ASP.NET creates the page instance, you can't use the lifecycle events like `OnActivating` to your advantage either. At some point you will need to reference the container directly, as you've done in `OnPreInit`; if you want to use parameters, you have to resolve and set the properties yourself instead of relying on `InjectProperties`, i.e. `Presenter = cp.RequestLifetime.Resolve(...parameters...);` – Bryan Watts Oct 06 '11 at 13:46
That's in fact the crux of the problem if I need to bind parameters: having to get back to a service locator pattern with the use of Resolve, instead of a general solution where I simply ask the container to inject the dependencies at the property level. – Fab60 Oct 06 '11 at 15:05
Right. I was indicating that it may be your only choice, since ASP.NET limits your options. I don't think there is a way to tell Autofac about parameters in the `InjectProperties` call, which is the only way I could see this working. Normally parameters are in scope for one `Resolve` call, but for properties there are potentially many of them. I'm not sure how you can get away from SL. – Bryan Watts Oct 06 '11 at 15:44

Stephen Phillip Baldwin · Answer 2 · 2013-08-29T02:37:27.800

This works and is automatic in Autofac

<Autofac.Integration.Web.Forms.InjectUnsetProperties()>
Public MustInherit Class ViewBasePage(Of TPresenter As BasePresenter(Of TView, TPresenter), TView As {IView, Class})
    Inherits System.Web.UI.Page
    Implements IView

Protected _presenter As TPresenter
Private _factory As Func(Of TView, TPresenter)

Public Property PresenterFactory As Func(Of TView, TPresenter)
   Get
      Return _factory
   End Get
   Set(value As Func(Of TView, TPresenter)
      _factory = value

      _presenter = _factory(DirectCast(DirectCast(Me, IView), TView))
   End Set
 End Property

Autofac Webform Integration: Manual Property Injection

2 Answers2