Question

suppose i have small wcf service which has duplex connection and i want that no method will be callback at my client end rather a event should fire instead. then how to restructure my code. my code as follows.

server end

namespace CommonParts
{
[ServiceContract(Namespace = "rf.services", 
    CallbackContract = typeof(IDataOutputCallback), 
    SessionMode = SessionMode.Required)]
public interface IServerWithCallback
{
    [OperationContract(IsOneWay=true)]
    void StartDataOutput(string msg);
}


public interface IDataOutputCallback {
    [OperationContract(IsOneWay = true)]
    void SendDataPacket(string data);
}
}

namespace RF.WCF.Callback.Server
{
class ServerWCallbackImpl : IServerWithCallback
{
    #region IServerWithCallback Members

    public void StartDataOutput(string msg)
    {
        //OperationContext.Current.
        IDataOutputCallback callback = OperationContext.Current.GetCallbackChannel<IDataOutputCallback>();
        for (int i = 0; i < 10; i++)
        {
            Random r = new Random();
            int interval = r.Next(500,3000);
            System.Threading.Thread.Sleep(interval);
            //callback.SendDataPacket("Packet " + i.ToString());
            callback.SendDataPacket("Hello " + msg);
        }
        callback.SendDataPacket("Last packet is this one :)");
    }
    #endregion
}
}

class Program
{
    static void Main(string[] args)
    {
        var myBinding = new NetTcpBinding(SecurityMode.None);
        ServiceHost duplex = new ServiceHost(typeof(ServerWCallbackImpl));
        duplex.AddServiceEndpoint(typeof(IServerWithCallback),
            myBinding,
            "net.tcp://192.168.1.2:9080/DataService");
        duplex.Open();
        Console.WriteLine("Host is running, press <ENTER> to exit.");
        Console.ReadLine();
        duplex.Close();
    }
}

client end

class CallbackImpl : IDataOutputCallback

{
#region IDataOutputCallback Members

public void SendDataPacket(string data)
{
  Console.WriteLine("Server sent: {0}", data);
}

#endregion

}

static void Main(string[] args)
{
    var myBinding = new NetTcpBinding(SecurityMode.None);
  DuplexChannelFactory<IServerWithCallback> cf =
          new DuplexChannelFactory<IServerWithCallback>(
              new CallbackImpl(),
              myBinding,
              new EndpointAddress("net.tcp://192.168.1.2:9080/DataService")); 
  IServerWithCallback srv = cf.CreateChannel();
  Console.Write("Enter Value... ");
  srv.StartDataOutput(Console.ReadLine());
  Console.WriteLine("Start");
  Console.ReadLine();
}

when this below line will be executed from client side called srv.StartDataOutput(Console.ReadLine());

then StartDataOutput() function will be called and from this function a callback function will be invoke called callback.SendDataPacket(“Hello ” + msg); then SendDataPacket() function will be called at client side.

so my question is how can i trigger a event at client side instead of callback function

Answer 1

A good tutorial for event-driven WCF asynchronous services is here at Code Project.
It should get you a good start on what you need done. One of the key statements made in this example is that the process is not too different from making a callback call. 🙂