I recently created a WCF service (dll) and a service host (exe). I know my WCF service is working correctly since I am able to successfully add the service to WcfTestClient.
One crucial thing to remember for those working with a Console application to host the WCF service is that the Web.config file in the WCF project is completely ignored. If your system.serviceModel configuration is there, then you need to move that section of config to the App.config of your Console project.
This is in addition to the answers concerning ensuring the namespace is specified in the right places.