When creating a WCF Service Application for your Silverlight application you will encounter a "cross domain" error with default configurations.
Below I show the default Service application code (only class name changed) and made the necessary Silverlight WCF configuration change for basicHttpBinding as shown by the arrow.
I then created a Web Service reference for both my Silverlight application and Test application. Note that Silverlight uses Async calls while the Test project uses Sync call to obtain data.
When I run the Silverlight application I get the following error:
I added the following clientaccesspolicy.xml file per THIS LINK (you can copy code from it) to my WCF Service and both my Silverlight and Unit test run without issue.
WCFService.zip (709.94 kb) <= SOURCE CODE