Dependency Injection in Web Forms MVC
time to read 3 min | 583 words

David Hayden has a post about the issue that you face when you are trying to use dependency injection in Web Forms MVC. I talked about similar issues here.

He points out that this type of code is bad:

    protected Page_PreInit(object sender, EventArgs e)
    {
            // Constructor Injection of Data Access Service and View
            ICustomerDAO dao = Container.Resolve<ICustomerDAO>():
            _presenter = new AddCustomerPresenter(dao, this);
            
            // Property Injection of Logging
            ILoggingService logger = Container.Resolve<ILoggingService>():
            _presenter.Logger = logger;
    }

This type of code a Worst Practice in my opinion. It means that the view is responsible for setting up the presenter, that is a big No! right there.

He gives the example of WCSF & Object Builder way of doing it, but I don't think that this is a good approach:

public partial class AddCustomer : Page, IAddCustomer
{
    private AddCustomerPresenter _presenter;

    [CreateNew]
    public AddCustomerPresenter Presenter
    {
        set
        {
            this._presenter = value;
            this._presenter.View = this;
        }
    }
    
    // ...
}

The problems that I have with this approach is that the view suddenly makes assumptions about the life cycle of the controller, which is not something that I want it to do. I may want a controller per conversation, for instance, and then where would I be? Another issue is that the view is responsible for injecting itself to presenter, which is not something that I would like to see there as well.

Here is how I do it with Rhino.Igloo:

public partial class AddCustomer : BasePage, IAddCustomer
{
    private AddCustomerPresenter _presenter;

    public AddCustomerPresenter Presenter
    {
        set
        {
            this._presenter = value;
        }
    }
    
    // ...
}

The BijectionFacility will notice that we have a settable property of type that inherit from BaseController, and will get it from the container and inject that in. I don't believe in explicit Controller->View communication, but assuming that I needed that, it would be very easy to inject that into the presenter. Very easy as in adding three lines of code to ComponentRepository's InjectControllers method:

PropertyInfo view = controller.GetType().GetProperty("View");
if(view!=null)
	view.SetValue(controller, instance);
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