Debug cryptic WCF errors with WCF Tracing and the Microsoft Service Trace Viewer

Some thoughts scribbled down on Monday 16 February 2009 at 01:13 PM

While working on a project involving Silverlight and WCF REST I ran into some errors that didn't give me much insight into the actual problem.

The error I got was:

System.Net.WebException: The remote server return an error: NotFound

The usual culprit is the message returning data greater than the default MaxMessageSize of 64K. In my case I was sure my message less than that.

I followed the following procedure to debug this error:

1. Enable tracing in WCF through the web.config
   

   <system.diagnostics>
       <sources>
         <source name="System.ServiceModel" switchValue="Information, ActivityTracing" propagateActivity="true">
           <listeners>
             <add name="traceListener" type="System.Diagnostics.XmlWriterTraceListener" initializeData="c:\log.svclog"></add>
           </listeners>
         </source>      
       </sources>
     </system.diagnostics>
   

1. Run the application and trigger the error
2. Open the log file (c:\log.svclog)
3. Microsoft Service Trace Viewer will open up
4. Navigate to the activity that caused the error
5. See the stack trace
   

In my case the error was a DateTime issue. One of my date fields was not set and hence defaults to 0001-01-01 and hence couldn't be serialized when it returns to the client.

In most cases if you get this type of error it usually is a serialization error.