系统.调用WCF服务时出现InvalidOperationException异常

我试图用netttcpbinding创建一个WCF回调服务。当我尝试调用服务的方法时，我得到以下异常:

An unhandled exception of type 'System.InvalidOperationException' occurred in System.ServiceModel.dll
Additional information: The InstanceContext provided to the ChannelFactory contains a UserObject that does not implement the CallbackContractType 'Client.WCFService.IHostFunctionsCallback'.

我添加了一个服务参考，而不是使用SvcUtil.exe我已经在网上搜索解决这个问题，但我还没有找到一个解决方案。

这是我的实现:

IHostFunctions.cs(部分的HostLibrary)

using System.ServiceModel;
namespace HostLibrary
{
    [ServiceContract(CallbackContract = typeof(ICallback))]
    public interface IHostFunctions
    {
        [OperationContract]
        void OpenSession();
    }
}

ICallback.cs(部分的HostLibrary)

using System.ServiceModel;
namespace HostLibrary
{
    public interface ICallback
    {
        [OperationContract]
        void OnCallback();
    }
}

HostFunctions.cs(部分的HostLibrary)

using System;
using System.ServiceModel;
using System.Timers;
namespace HostLibrary
{
    [ServiceBehavior(ConcurrencyMode = ConcurrencyMode.Multiple)]
    public class HostFunctions : IHostFunctions
    {
        #region Implementation of IHostFunctions
        public static ICallback Callback;
        public static Timer Timer;
        public void OpenSession()
        {
            Console.WriteLine("> Session opened at {0}", DateTime.Now);
            Callback = OperationContext.Current.GetCallbackChannel<ICallback>();
            Timer = new Timer(1000);
            Timer.Elapsed += OnTimerElapsed;
            Timer.Enabled = true;
        }
        void OnTimerElapsed(object sender, ElapsedEventArgs e)
        {
            Callback.OnCallback();
        }
        #endregion
    }
}

Callback.cs (Part of Client)

using System;
using HostLibrary;
namespace Client
{
    public class Callback : ICallback
    {
        #region Implementation of ICallback
        public void OnCallback()
        {
            Console.WriteLine("> Received callback at {0}", DateTime.Now);
        }
        #endregion
    }
}

服务的Program.cs

using System;
using System.ServiceModel;
using HostLibrary;
namespace WCF_TCP_Callbacks
{
    internal static class Program
    {
        private static void Main(string[] args)
        {
            using (var sh = new ServiceHost(typeof (HostFunctions)))
            {
                sh.Open();
                Console.WriteLine("Service started.");
                Console.ReadLine();
                Console.WriteLine("Stopping service...");
                sh.Close();
            }
        }
    }
}

客户端的Program.cs

using System;
using System.Globalization;
using System.ServiceModel;
using System.Threading;
using Client.WCFService;
namespace Client
{
    internal class Program
    {
        private static void Main(string[] args)
        {
            var callback = new Callback();
            using (var proxy = new HostFunctionsClient(new InstanceContext(callback)))
            {
                proxy.OpenSession();
            }
            Console.ReadLine();
        }
    }
}

代码来自http://adamprescott.net/2012/08/15/a-simple-wcf-service-callback-example/，但是使用了netttcpbinding。

[CallbackBehavior(ConcurrencyMode=ConcurrencyMode.Reentrant, UseSynchronizationContext=false)]
public class Callback : ICallback
{
  ....
}

Callback : ICallback

Client.WCFService.IHostFunctionsCallback