Exception when calling the authentication service

   Helo,
I've got an application WPF that uses a web server for accessing the DB,I also use devorce application framework...
when I call the login

public void Login()
     {
         var loginCredential = new LoginCredential(_userName, _password, "");

         bool isLogged = false;
         try
         {
             _authenticationService.Login(loginCredential);
             _eventAggregator.Publish(new ActivateWorkspaceMessage());

         }
         catch (LoginException ex)
         {
            //todo add logic for message
             int i = 0;
         }

     }

I got this exception: 

Type 'my.DomainModel.CustomerSearchResult' cannot be added to list of known types since another type 'my.DomainModel.CustomerSearchResult' with the same data contract name 'http://schemas.datacontract.org/2004/07/my.DomainModel:CustomerSearchResult' is already present. If there are different collections of a particular type - for example, List<Test> and Test[], they cannot both be added as known types.  Consider specifying only one of these types for addition to the known types list.

I think the problem is due to the fact my WPF application uses my.Client, while Web uses my.Server that contains the edmx and shares between my.Client the mymodel.IB.Designer.cs... 

Any suggestion?
Thanks