我所知道的CallbackContract in WCF

参考网址：https://www.cnblogs.com/scy251147/archive/2012/11/26/2789432.html

由于WCF中提供了CallbackContract属性，所以在双工通信中，我们可以很方便的和Server进行通信。虽然查遍了MSDN，也看过了它提供的例子，但是还是不知道怎么来使用(因为MSDN中只是给你提供了Server端的调用方法，并没有客户端的调用方式，所以例子没法儿跑起来，当然也就不能够从示例中看出CallbackContract属性的工作方式，鄙视下，呵呵)。在这篇文章中，我要做的就是让这个例子能够顺利地跑起来，从而了解CallbackContract的工作方式。

服务端编写

首先，创建一个名称为CallbackContractWCF的控制台项目，添加一个DuplexHello类作为我们的Service，具体代码就Copy了MSDN上面的：

using System;
using System.ServiceModel;
using System.Threading;

namespace CallbackContractWCF
{
    [ServiceContract(Name = "SampleDuplexHello", CallbackContract = typeof(IHelloCallbackContract), SessionMode = SessionMode.Required)]
    public interface IDuplexHello
    {
        [OperationContract(IsOneWay = true)]
        void Hello(string greeting);
    }

    public interface IHelloCallbackContract
    {
        [OperationContract(IsOneWay = true)]
        void Reply(string responseToGreeting);
    }

    public class DuplexHello:IDuplexHello
    {
        public DuplexHello()
        {
            Console.WriteLine("Service object created: " + this.GetHashCode().ToString());
        }

        ~DuplexHello()
        {
            Console.WriteLine("Service object distroyed: " + this.GetHashCode().ToString());
        }

        public void Hello(string greeting)
        {
            Console.WriteLine("Caller sent: "+greeting);
            Console.WriteLine("Session ID: "+OperationContext.Current.SessionId);
            Console.WriteLine("Waiting two seconds before returning call.");
            Thread.Sleep(2000);
            IHelloCallbackContract callerProxy = OperationContext.Current.GetCallbackChannel<IHelloCallbackContract>();
            string response = "Service object " + this.GetHashCode().ToString() + " received." + greeting;
            Console.WriteLine("Sending back: " + response);
            callerProxy.Reply(response);
        }
    }
}

using System;
using System.ServiceModel;
using System.Threading;

namespace CallbackContractWCF
{
    [ServiceContract(Name = "SampleDuplexHello", CallbackContract = typeof(IHelloCallbackContract), SessionMode = SessionMode.Required)]
    public interface IDuplexHello
    {
        [OperationContract(IsOneWay = true)]
        void Hello(string greeting);
    }

    public interface IHelloCallbackContract
    {
        [OperationContract(IsOneWay = true)]
        void Reply(string responseToGreeting);
    }

    public class DuplexHello:IDuplexHello
    {
        public DuplexHello()
        {
            Console.WriteLine("Service object created: " + this.GetHashCode().ToString());
        }

        ~DuplexHello()
        {
            Console.WriteLine("Service object distroyed: " + this.GetHashCode().ToString());
        }

        public void Hello(string greeting)
        {
            Console.WriteLine("Caller sent: "+greeting);
            Console.WriteLine("Session ID: "+OperationContext.Current.SessionId);
            Console.WriteLine("Waiting two seconds before returning call.");
            Thread.Sleep(2000);
            IHelloCallbackContract callerProxy = OperationContext.Current.GetCallbackChannel<IHelloCallbackContract>();
            string response = "Service object " + this.GetHashCode().ToString() + " received." + greeting;
            Console.WriteLine("Sending back: " + response);
            callerProxy.Reply(response);
        }
    }
}

从这个类中，我们可以看到它有一个IHelloCallbackContract的接口，由于它在ServiceContract中被标记为CallbackContract = typeof(IHelloCallbackContract)，所以它用于客户端回调。意即，服务端可以通过此接口中的方法将数据发送给客户端，客户端只需要实现此接口，即可接收到服务端发送过来的消息。

然后是创建配置文件，请参见我的文章：基于net.tcp的WCF配置实例解析。这里我们使用的EndPoint为：net.tcp://127.0.0.1/DuplexHello，创建好App.config配置文件后，拷贝到CallbackContractWCF项目下，然后打开Program.cs文件，编码以便让服务端能够启动监听：

using (ServiceHost host = new ServiceHost(typeof(DuplexHello)))
            {
                ServiceMetadataBehavior smb = host.Description.Behaviors.Find<ServiceMetadataBehavior>();
                if (smb == null)
                {
                    host.Description.Behaviors.Add(new ServiceMetadataBehavior());
                }
//暴露MetaData，以便能够让SvcUtil.exe工具生成客户端代理类和配置文件
                host.AddServiceEndpoint(typeof(IMetadataExchange), MetadataExchangeBindings.CreateMexTcpBinding(), "mex");
                host.Open();
                Console.WriteLine("service listen on endpoint ...");
                Console.WriteLine("Press ENTER to stop ...");
                Console.ReadLine();
                host.Abort();
                host.Close();
            }

using (ServiceHost host = new ServiceHost(typeof(DuplexHello)))
            {
                ServiceMetadataBehavior smb = host.Description.Behaviors.Find<ServiceMetadataBehavior>();
                if (smb == null)
                {
                    host.Description.Behaviors.Add(new ServiceMetadataBehavior());
                }
//暴露MetaData，以便能够让SvcUtil.exe工具生成客户端代理类和配置文件
                host.AddServiceEndpoint(typeof(IMetadataExchange), MetadataExchangeBindings.CreateMexTcpBinding(), "mex");
                host.Open();
                Console.WriteLine("service listen on endpoint ...");
                Console.WriteLine("Press ENTER to stop ...");
                Console.ReadLine();
                host.Abort();
                host.Close();
            }

好了，启动服务端，我们可以看到如下界面，服务端启动成功了：

客户端编写 

下面开始来编写客户端。

首先打开SvcUtil.exe，按照文章：基于net.tcp的WCF配置实例解析 中介绍的方法，生成output.config文件和DuplexHello.cs代理类文件。

其次创建一个名称为CallbackContractWCFClient的Windows Form Application项目，将上面的两个文件拷贝进来，并修改output.config名称为App.config。

然后打开ClientForm窗体，继承自SampleDuplexHelloCallback接口(这个接口也就是服务端的IHelloCallbackContract接口的代理)，然后编写以下代码进行数据发送和接收：

using System;
using System.Windows.Forms;
using System.ServiceModel;

namespace CallbackContractWCFClient
{
    public partial class ClientForm : Form, SampleDuplexHelloCallback
    {
        public ClientForm()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            InstanceContext site = new InstanceContext(this);
            SampleDuplexHelloClient client = new SampleDuplexHelloClient(site);

            string msg =" This is a Client Message sent to Server side...";
            label1.Text = "Client Sent: " + msg;
            client.Hello(msg);
           
        }

        public void Reply(string responseToGreeting)
        {
            label2.Text = "Server Reply: " + responseToGreeting;
        }

    }
}

using System;
using System.Windows.Forms;
using System.ServiceModel;

namespace CallbackContractWCFClient
{
    public partial class ClientForm : Form, SampleDuplexHelloCallback
    {
        public ClientForm()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            InstanceContext site = new InstanceContext(this);
            SampleDuplexHelloClient client = new SampleDuplexHelloClient(site);

            string msg =" This is a Client Message sent to Server side...";
            label1.Text = "Client Sent: " + msg;
            client.Hello(msg);
           
        }

        public void Reply(string responseToGreeting)
        {
            label2.Text = "Server Reply: " + responseToGreeting;
        }

    }
}

这样，我们的服务端和客户端就写好了，接下来运行，结果显示如下：

服务端：

 客户端：

源码下载

点击这里下载

 

 

分类: WCF 点滴记录