title: How to make a WCF service support multiple callback?
body: <p>I have a nettcp WCF service that supports single callback method.</p>
  
  <p>I want to add new callback methods by adding new interface that contains the new methods without breaking the old one as there is another things depend on the old interface.</p>
  
  <p>I tried to add new interface that inherits from the old one but the gerenated proxy in the the client application does not contain the old callback interface.</p>
  
  <p>the code is as follows </p>
  
  <pre><code>interface IOldCallback
      {
          [OperationContract(IsOneWay = true)]
          void OnMethod1(int x);
      }
  
  interface INewCallback : IOldCallback
  {
  [OperationContract(IsOneWay = true)]
          void OnMethod2(float x);
  
  [OperationContract(IsOneWay = true)]
          void OnMethod3(bool x);
  
  
  }
   [ServiceContract(SessionMode = SessionMode.Required, CallbackContract = typeof(INewCallback))]
      public interface IMyService
  {
  }
  </code></pre>
  
  <p>P.S</p>
  
  <p>I make quick and dirty solution so I'll not break the old client codes</p>
  
  <pre><code>interface INewCallback : IOldCallback
  {
  [OperationContract(IsOneWay = true)]
          void OnMethod2(float x);
  
  [OperationContract(IsOneWay = true)]
          void OnMethod3(bool x);
  
  [OperationContract(IsOneWay = true)]
         new void OnMethod1(int x);
  
  
  }
  </code></pre>