I have a VB6 application that needs to communicate with a VS2008 VB.NET WCF server. I have built a VB.NET WCF DLL to be used on the client side, and it --almost-- works with the VB6 application. When I try to run the VB6 app in debug mode, I get "Could not find endpoint element with name 'NetTCPBinding_IComPortManager' and contract 'IComPortManager' in the ServiceModel client configuration section." Using a dummy VB.Net client app, with the same WCF DLL works fine. I presume that the VB6 app/WCF DLL is not finding app.config. Where should app.config be ? Is there a way to tell WCF where to find app.config ?