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copied!<p>Interesting problem.</p> <p><code>WithEvents</code> property on automation creates the handler and attaches it to <code>Elapsed</code> delegate, so this one is not <code>NULL</code> - hence no exception</p> <p>However, when <code>WithEvents</code> is <code>No</code>, and <code>Timer.Start()</code> is invoked, as you rightly say no exception bubbles up, even though (in theory) <code>Elapsed</code> delegate is null.</p> <p>The simple explanation to this would be, that NAV attaches empty delegate regardless of <code>WithEvents</code> property. To support that, if you put code in <code>Timer::Elapsed()</code> trigger, then take off <code>WithEvents</code>, and bring it back - the code will still be there (i.e. trigger still exists in unchanged form), which makes me lean towards conclusion that it exists always (i.e. empty delegate).</p> <p>But of course it's NAV so it couldn't be that simple.</p> <p>I created a test codeunit from above MSDN example, but made a small change to the automation:</p> <pre><code>/// <summary> /// Whenever the internal timer elapses, an event must be fired /// </summary> private void mTimer_Elapsed(object sender, ElapsedEventArgs e) { OnElapsed(EventArgs.Empty); throw null; } </code></pre> <p>This, in theory, should throw <code>NULL</code> whenever <code>mTimer_Elapsed</code> is invoked - nothing however bubbles up in NAV. I went a bit further and changed this:</p> <pre><code>///<summary> /// Invoke the Changed event; called whenever the internal timer elapses /// </summary> protected virtual void OnElapsed(EventArgs e) { throw new InvalidCastException("test"); //Elapsed(); } </code></pre> <p>Again, nothing happens in NAV.</p> <p>Note, that both changes behave as expected if the <code>COM Timer</code> is consumed from within .NET project. This makes me think, that NAV Interop must be capturing exceptions from the automation and handle them internally.</p> <p>I would however pop that question in <a href="http://mibuso.com/" rel="nofollow">Mibuso</a> - someone there will probably know better.</p>

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