Leblanc Meneses has published a great, very detailed post explaining
configuration in Silverlight and a standalone file uploader.
ConfigurationManager, the commonly used .NET configuration API, is unavailable in Silverlight applications. The minimum code option is to deserialize an XML configuration file, or to read from initParams.
While most Silverlight applications only need Service endpoints updated in ServiceReferences.ClientConfig, there are occasions where a PRISM module may be needed to support reconfiguration. When this happens, I use an MSBuild task to create and/or merge the correct settings into a module.xml within the PRISM module, using a strongly typed object representing the XML file. I also deserialize the XML file to retrieve its values.