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POTraceSource.TraceEvent() fails logging when Exception message contains non-printable characters
 

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    <p>I have a call to <code>TraceSource.TraceEvent()</code> that is sometimes not writing to the Azure Diagnostics logs.</p> <pre><code>public class WorkerRole : RoleEntryPoint { private TraceSource trace = new TraceSource( "ImportService", SourceLevels.Information); public override void Run() { ... try { ... } catch (Exception ex) { bool hasMsg = !string.IsNullOrEmpty(ex.Message); trace.TraceEvent(TraceEventType.Error, 0, "ex has message: " + hasMsg.ToString()); // this gets logged trace.TraceEvent(TraceEventType.Error, 0, "Inner exception message: " + ex.Message); // this does not } } } </code></pre> <p>In certain cases, and I can't tell which since I can't read the Exception message, the second call is not found in the WADLogsTable. Are there certain characters that are not allowed, either by <code>TraceSource</code> or by <code>DiagnosticMonitor</code>?</p> <p>To further narrow this down, the Exception in question is actually the <code>InnerException</code> of Exception: "There is an error in XML document (72, -499)". The XML that causes the Exception contains invalid character entities, eg <code>&amp;#x11;</code>. Could it be that the Exception message contains some of these character entities and the <code>TraceSource</code> fails to log them?</p> <p><strong>Edit:</strong> I was able to finally repro this in my dev environment and so I was able to examine the Exception in the debugger. The exception that won't log is an <code>XmlException</code>:</p> <blockquote> <p>'', hexadecimal value 0x11, is an invalid character. Line 72, position -499.</p> </blockquote> <p>In between the quotes is the non-printable character - it shows up as a black triangle in the debugger. So, this leads me to believe that my suspicion is correct - Some piece of the logging mechanism doesn't like the non-printable character. So, which piece? Or, more importantly, since it looks like I need to start sanitizing all of my strings when tracing, which characters should I look for to remove?</p> <p>Is there some built in function that will sanitize a string, removing non-printable characters?</p>
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