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POMVP, Winforms - EventHandlers or Delegates
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  1. POMVP, Winforms - EventHandlers or Delegates
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    copied!<p>I have implemented the MVP pattern in a few WinForms applications that uses a passive view. I implement an interface containing properties and delegates in the form of Action&lt; T > and Func&lt; T > to wire up UI events in concrete views and call back to the presenter.</p> <p>I am about to start a new project and did a little research into the pattern online including the many examples of the pattern here and notice that the all use EventHandler to notify presenters.</p> <p>I don't really understand why events would be used in this case, since I see a view as only having one presenter.</p> <p>My question is, is this for the sake of remaining consistent with how the .Net framework uses events, or for some other reason that I am not seeing?</p> <p>Here is a trivial example of the pattern I use:</p> <pre><code>public interface IViewAbstraction { public ModelData ModelData { set; } public Action&lt;ModelData&gt; ModelDataChangedCallback { set; } } public class SomeWinForm : Form, IViewAbstraction { private Action&lt;ModelData&gt; modelDataChanged; private ModelData model; public ModelData ModelData { set { /* when this property changes, update UI */ } } public Action&lt;ModelData&gt; ModelDataChangedCallback { set { modelDataChanged = value; } } private void OnSomeWinformsEvent(EventArgs args) { if (modelDataChanged == null) throw new Exception(); modelDataChanged(model); } } public class Presenter { private readonly IViewAbstraction view; private readonly IDataLayerAbstraction dataLayer; public Presenter(IViewAbstraction view, IDataLayerAbstraction dataLayer) { this.dataLayer = dataLayer; this.view = view; this.view.ModelDataChangedCallback = OnModelChanged; this.view.ModelData = dataLayer.GetData(); } private void OnModelChanged(ModelData data) { // validate and save data. } } </code></pre>
 

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