wpf with ef

Hi every body.

I'm using visual studio 2010 for creating wpf application.for the model I use EF  in other project as a classlibrary and refrence it to my application.I copied the app.config from the class library to my application but still raise an error :

The specified named connection is either not found in the configuration, not intended to be used with the EntityClient provider, or not valid.

could you help me?

so thanks.