title: Applying ServiceContract and OperationContract on existing interfaces
body: <p>I have some existing interfaces that are used over all over system. </p>
  
  <p>Now I want to use one of the interfaces to be as service contract.</p>
  
  <p>But the problem is that I need to add <code>[ServiceContract]</code> and <code>[OperationContract]</code> attributes on existing interfaces and they will contaminate the rest of the code .</p>
  
  <p>Any solution to this problem with out duplicating the interfaces?</p>
  
  <p>Applying the attributes on the concrete implementation ? is that a good practice ?</p>
  
  <p>Thanks </p>