>You could :

   public partial class PluczExp_PluczContext  : DbContext
>    {
>        public PluczExp_PluczContext (): base("name=PluczExpEntities") {}
>
>        public PluczExp_PluczContext (string ConnectionName): base("name="+ConnectionName) {}
>    }

so instantiating the context with an empty constructor would use the "PluczExpEntities" connection name in app.config and instantiating with

PluczExp_PluczContext  PGD = new PluczExp_PluczContext ("PluczExpEntities2");

would use the connection named 'PluczExpEntities2'. In app.config just copy the default, rename and adjust.

Yes. I got it to work to what I want.

What did not work is that I created a partial class (containing the constructor with one parameter) in a different assembly.

But I created that partial class (containing the constructor with one parameter) in the same assembly as the one generated by EF. Even if I regenerate the EF stuff, that class should not be affected.

Thanks for your help.