Monday, January 10, 2011

Debugging WCF

I'm relatively new to the world of Microsoft foundation libraries.  For the most part I am impressed, but I cannot understand the idea of development libraries doing their best to hide errors from you unless you first speak the magic rites (I would have thought there ought to be magic rites to cause error hiding, not the other way around).  Anyway, WCF -- Windows Communications Foundation -- is a pretty good RPC system which has this property.  To turn on tracing so you can debug your application, follow this advice:
After some Live Searching (i was actually googling, but let’s make Microsoft think at least someone outside of Redmond uses Live Search) i discovered that you can enable WCF tracing. Bingo! Why didn’t Juval Lowy’s book mention this? It’s supposed to be the WCF Bible…. Oh well, thanks to Google, i mean Live Search, we now know how to enable WCF’s tracing:

    <trace autoflush="true" />
      <source name="System.ServiceModel"
              switchValue="Information, ActivityTracing"
          <add name="wcfTraceListener" type="System.Diagnostics.XmlWriterTraceListener"initializeData="WcfTrace.svclog" />

You can also use the Service Configuration Editor tool which is available in the Windows SDK, but spare yourself the pain of that tool and just copy/paste this xml in your config file.
Now run the service again, and do whatever it was that triggered the weird client-side exception. After the exception occurred, open the WcfTrace.svclog file with either an editor (it’s not very readable though) or with the Microsoft Service Trace Viewer tool (which is not too bad actually).