Question

I’m trying to get WCF duplex communication working an I’m struggling as I keep getting the error:

The InstanceContext provide to the ChannelFactory contains a UserObject that does not implement the CallbackContractType”

I know there are other posts on the subject but couldnt relate them to my exact problem so thought I’d post myself.

Here’s my code, I’ve only included the bits I think are relevant but please let me know if you require anything else:

Host interface definitions

[ServiceContract(CallbackContract = typeof(IDataCollectorCallback), SessionMode = SessionMode.Required)]
  public interface IDataCollector
  {
    [OperationContract(IsOneWay = true)]
    void GetData();
  }

  public interface IDataCollectorCallback
  {
    [OperationContract(IsOneWay = true)]
    void returnData();
  }

Implementation of service

public class DataCollector : IDataCollector 
  { 
    public void GetData() 
    {

      Console.WriteLine("Getting data"); 
      Console.WriteLine("Waiting");
      System.Threading.Thread.Sleep(10000);
      Console.WriteLine("Sending Data back");
      Callback.returnData();


    }

    IDataCollectorCallback Callback
    {
      get
      {
        return OperationContext.Current.GetCallbackChannel<IDataCollectorCallback>();
      }
    }

  }

Client code

class Program
  {
    static void Main(string[] args) 
    { 
      // while (true) 
      //{ 
        Console.WriteLine("Press enter to trigger data collection");
        Console.ReadLine();
        InstanceContext context = new InstanceContext(new MyCallback());


        AshService.DataCollectorClient svc = new AshService.DataCollectorClient(context);

        svc.GetData();
        Console.WriteLine("awaiting data coming back");
        Console.ReadLine();
      //} 
    }

  }

  class MyCallback : IDataCollectorCallback
  {
    public MyCallback()
    {
    }

    public void returnData()
    {
      Console.WriteLine("Got Data back from the server");
    }
  }

To get a reference to the IDataCollector interface I have included a ref to the dll in the host project. I’m wondering if this is where my issue lies. Do I need to redeclare the callback interface in the client application?

Please let me know if you require anything else.

Kind Regards

Ash

Answer 1

Apologies.

I have worked out the answer.

My problem was that I was referencing the dll containing the callback interface.

What I should have done is this….

    class MyCallback : AshService.IDataCollectorCallback

Thanks

Ash