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POBetter way to show error messages in async methods
 

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  1. POBetter way to show error messages in async methods
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    <p>The fact that we can't use the <code>await</code> keyword in <code>catch</code> blocks makes it quite awkward to show error messages from async methods in WinRT, since the <code>MessageDialog</code> API is asynchronous. Ideally I would like be able to write this:</p> <pre><code> private async Task DoSomethingAsync() { try { // Some code that can throw an exception ... } catch (Exception ex) { var dialog = new MessageDialog("Something went wrong!"); await dialog.ShowAsync(); } } </code></pre> <p>But instead I have to write it like this:</p> <pre><code> private async Task DoSomethingAsync() { bool error = false; try { // Some code that can throw an exception ... } catch (Exception ex) { error = true; } if (error) { var dialog = new MessageDialog("Something went wrong!"); await dialog.ShowAsync(); } } </code></pre> <p>All methods that need to do this have to follow a similar pattern, which I really don't like, because it reduces the code readability.</p> <p>Is there a better way to handle this?</p> <hr> <p><em>EDIT:</em> I came up with this (which is similar to what svick suggested in his comments):</p> <pre><code>static class Async { public static async Task Try(Func&lt;Task&gt; asyncAction) { await asyncAction(); } public static async Task Catch&lt;TException&gt;(this Task task, Func&lt;TException, Task&gt; handleExceptionAsync, bool rethrow = false) where TException : Exception { TException exception = null; try { await task; } catch (TException ex) { exception = ex; } if (exception != null) { await handleExceptionAsync(exception); if (rethrow) ExceptionDispatchInfo.Capture(exception).Throw(); } } } </code></pre> <p>Usage:</p> <pre><code>private async Task DoSomethingAsync() { await Async.Try(async () =&gt; { // Some code that can throw an exception ... }) .Catch&lt;Exception&gt;(async ex =&gt; { var dialog = new MessageDialog("Something went wrong!"); await dialog.ShowAsync(); }); } </code></pre> <p><code>.Catch&lt;...&gt;</code> calls can be chained to mimick multiple <code>catch</code> blocks.</p> <p>But I'm not really happy with this solution; the syntax is even more awkward than before...</p>
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    1. USThomas Levesque
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    1. COCouldn't you just encapsulate that into a method? Something like `AsyncTryCatch(async () => /* Some code that can throw an exception */, async ex => /* error handling */)`.
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    2. CODo you really need to show a message box? Perhaps something like a message panel where you print exceptions would do?
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    3. CO@svick, yes, I thought of something like that, but it's still not very convenient; for instance, it doesn't support multiple catch clauses, and doesn't tell me whether the operation succeeded.
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