This is one purely for a search engine. If you’re ever looking at WCF and adding a BehaviorExtensionElement in order to add custom behaviors then take care if you see an error message like; "Verify that the extension is registered in the extension collection at system.serviceModel/extensions/behaviorExtensions" It looks like a bug ( see report here and here ) in that if you use a typename like this in your config file; <extensions> <behaviorExtensions> <add name="clientInterception" type="ProductsApplication.MyInspector,ProductsApplication, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null"/> </behaviorExtensions> </extensions> then you’ll see a failure whereas if you use one like this; <extensions> <behaviorExtensions> <add name="clientInterception" type="ProductsApplication...