What is a good way to implement events in Passive View?

Question

Hi,

I am learning the Passive View pattern to keep my C# WinForms application easier to test and maintain.

It has worked well so far but I wonder if there is a better way to implement Events than the way I am doing it now (and keeping them testable). This is what it looks like (omitting code not relevant for this example). Basically what I am looking for if is there is a way to skip hooking up events both in the presenter and in the form, I would prefer doing all work in the presenter.

My view looks like this:

public interface IApplicationView
{
    event EventHandler Find;
}

My presenter looks like this:

public class ApplicationPresenter
{
    private IApplicationView _view;
    private IApplicationDomain _domain;

    public ApplicationPresenter(IApplicationView view) : this(view, new ApplicationDomain()) {}
    public ApplicationPresenter(IApplicationView view, IApplicationDomain domain) {
        _view = view;
        _domain = domain;

        HookupEventHandlersTo(view);
    }

    private void HookupEventHandlersTo(IApplicationView view)
    {
        view.Find += delegate { FindAction(); };
    }

    public void FindAction()
    {
        // ...
    }
}

My WinForm looks like:

public partial class Form1 : Form, IApplicationView
{
    private ApplicationPresenter _presenter;
    public event EventHandler Find = delegate {};

    public Form1()
    {
        InitializeComponent();
        _presenter = new ApplicationPresenter(this);
        HookupEvents();
    }

    private void HookupEvents()
    {
        searchButton.Click += Find;
    }
}

Thanks!

Answer 1

Check out this example of how to implement the Passive View. It has a good way of wiring/unwiring for events between the view and controller that puts most of the work in the controller.

Answer 2

Another great resource for learning MVP with WinForms is Jeremy Millers Build Your Own CAB series. I found this incredibly useful when I was learning,

The article on View to Presenter Communication will be useful to you; there is a good discussion here on using events vs making direct calls. Even better, the Event Aggregator article presents a "publish/subscribe" mechanism that can be used instead of events, while keeping the code testable. This is the approach that I personally prefer, and have had good success with.