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POSubscriber method vs event
 

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    <p>I have noticed a new tendency in .NET 4.0, specifically in potentially multi-threaded scenarios, which is avoiding events, and providing subscriber methods instead.</p> <p>For example, <a href="http://msdn.microsoft.com/en-us/library/system.threading.tasks.task.aspx" rel="nofollow">System.Threading.Tasks.Task</a> and <code>Task&lt;TResult&gt;</code> have <a href="http://msdn.microsoft.com/en-us/library/system.threading.tasks.task.continuewith.aspx" rel="nofollow">ContinueWith()</a> methods instead of a Completed or Finished event. Another example is <a href="http://msdn.microsoft.com/en-us/library/system.threading.cancellationtoken.aspx" rel="nofollow">System.Threading.CancellationToken</a>: it has a <a href="http://msdn.microsoft.com/en-us/library/system.threading.cancellationtoken.register%28VS.100%29.aspx" rel="nofollow">Register()</a> method instead of a CancellationRequested event.</p> <p>While Task.ContinueWith() is logical because it allows for easy task chaining (would not be so elegant with events), and that it also allows <code>Task&lt;TResult&gt;</code> to inherit from <code>Task</code> (because this way, <code>Task&lt;TResult&gt;</code> can provide appropriate overloads, which would not be possible for an event: if you have an event EventHandler Finished in Task, all you can do is create <em>another</em> event, say, event <code>EventHandler&lt;TaskResultEventArgs&gt;</code> Finished in <code>Task&lt;TResult&gt;</code>, which is not very nice), but I cannot find the same explanation for CancellationToken.Register().</p> <p>So, what are the disadvantages of events in similar scenarios? Should I also follow this pattern? To clarify, which one of the below should I choose? When should I prefer one against the other?</p> <pre><code>public event EventHandler Finished; // or public IDisposable OnFinished(Action continuation) </code></pre> <p>Thank you very much!</p>
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    1. CO@Jon Skeet: thanks, I didn't notice that my angel brackets needed some escaping.
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    2. COUI events etc can be posted using the UI message queue and can potentially be really slow/heavy compared to using a delegate or a simple Task..
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    3. CO@Barfieldmv: Action call could be posted using the same technique with Invoke/BeginInvoke to the UI thread. It's not the difference.
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      1. USIvan Danilov
 

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