This sample makes use of a WCF custom MessageInspector as described in the MSDN documentation. A message inspector is an extensibility object that can be used in the service model's client runtime and dispatch runtime programmatically or through configuration and that can inspect and alter messages after they are received or before they are sent. The sample here is derived from Oren Trutner's article “Signing Amazon Product Advertising API – C#/WCF.” Oren’s example is extended to allow all the configuration to occur in the application configuration (app.config) file. All of the Amazon helper methods have been moved to a separate library that can be used/referenced in any project. A separate console app has been included that demonstrates how to use the app.config file to configure the WCF endpoints and how to add the custom MessageInspector behavior to the endpoint.