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    <p>Normally, I'm not a big fan of centralized/global exception handling. My personal preference would be to either handle the exception everywhere or write your own proxy wrapper object that will handle/translate the expected fault exceptions.</p> <p>That said, there is an approach you can consider (though it requires modifying all your commands).</p> <p>First, factor the actual logic into an <code>async Task</code> method, as such:</p> <pre><code>public async Task MyCommandAsync() { try { using (var proxy = new MyProxy()) { var something = await proxy.GetSomethingAsync(); } } catch (FaultException&lt;MyFaultDetail&gt; ex) { // Do something here } } public async override void MyCommandImplementation() { MyCommandAsync(); } </code></pre> <p>Normally, I recommend implementing <code>async ICommand</code>s with an <code>async Task ExecuteAsync</code> method and matching <code>async void Execute</code> which will just do <code>await ExecuteAsync();</code>. The example I have above is almost the same except the <code>async void</code> method is <em>not</em> <code>await</code>ing the <code>Task</code>. This is dangerous and I'll explain below.</p> <p>Keeping your logic in an <code>async Task</code> gives you one tremendous advantage: you can unit test much more easily. Also, <code>async Task</code> methods have different exception handling which you can (ab)use to solve your problem.</p> <p>An <code>async Task</code> method - if the returned <code>Task</code> is never <code>await</code>ed - will raise <a href="http://msdn.microsoft.com/en-us/library/system.threading.tasks.taskscheduler.unobservedtaskexception.aspx" rel="nofollow"><code>TaskScheduler.UnobservedTaskException</code></a>. Note that this will <em>not</em> crash your process (as of .NET 4.5); your handler must decide the best response. Since your <code>async void</code> method is <em>not</em> <code>await</code>ing the <code>Task</code> returned by your <code>async Task</code> method, any exceptions will end up in <code>UnobservedTaskException</code>.</p> <p>So that will work, but it has one serious side effect: <em>any</em> unobserved <code>Task</code> exception will end up in the same handler (not just ones from your <code>ICommand</code>s). The reason that unobserved task exceptions were changed in .NET 4.5 to be ignored by default is because <em>that situation is no longer unusual</em> in <code>async</code> code. For example, consider this code which will attempt to download from two different urls and take the first response:</p> <pre><code>async Task&lt;string&gt; GetMyStringAsync() { var task1 = httpClient.GetAsync(url1); var task2 = httpClient.GetAsync(url2); var completedTask = await Task.WhenAny(task1, task2); return await completedTask; } </code></pre> <p>In this case, if the slower url results in an error, then that exception will be sent to <code>UnobservedTaskException</code>.</p>
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    1. POGlobally catch exceptions thrown from WCF async calls in a background thread
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    1. USStephen Cleary
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    1. POGlobally catch exceptions thrown from WCF async calls in a background thread
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    1. CO1/2 +1, thanks a lot for this answer, this is very helpful and well explained. I definitely agree with the "async Task MyCommandAsync" / "async override void MyCommandImplementation" pattern because as you said it makes the code much more testable. The `UnobservedTaskException` event is interesting, but kind of dangerous IMO. Its behavior changed between .Net4 and .Net4.5, and the event will only be raised when the GC does its job.
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    2. CO2/2 So the answer I think is to separate the `ICommand` implementation and the async processing in two methods. One does the async processing and returns a Task. The second one awaits the first and as I need a kind of global exception handling, I could write the logic once and call it using `await MyCommandAsync().ContinueWith(z => MyGlobalExceptionHandler(z.Exception)...);` in the second method.
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    3. COOh, btw, I just discovered you were the author of this [excellent article](http://msdn.microsoft.com/en-us/magazine/jj991977.aspx) on MSDN, thanks a lot :)
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