If you're a fan of Fiddler, you may have used it with prior versions of RIA Services to capture the traffic between your Silverlight client and your server side. This worked great in the past because RIA Services used a (somewhat bastardized) JSON encoding format.

But in the latest release of WCF RIA Services, the default encoding format is binary - which is not supported by Fiddler out of the box. Luckily, Samuel Jack has created a WCF Binary Inspector plug-in for Fiddler, which allows for examination of the new default encoding.

Here is how to setup Fiddler to capture traffic with WCF RIA Services:

Download and Install Fiddler

Download the Fiddler WCF Binary Inspector plugin

Extract BinaryMessageFiddlerExtension.dll and copy to the Fiddler Inspectors Directory, by default C:\Program Files\Fiddler2\Inspectors

Now, start up Fiddler – and then start up your RIA Services application. You’ll quickly notice that you’re not capturing any traffic L This is because Fiddler doesn’t capture from localhost by default. There are a variety of solutions to this, some of which may or may not work for your configuration.

The easiest solution that works for me is to append a period (“.”) just after localhost in your application's URL.

After that, you should see captured sessions as you make requests, and you can visit the "WCF Binary" tabs to see the request and response values, decoded.