WCF的双工模式

双工模式的特点

1.无论使用单向消息发送还是请求/答复消息发送方式，服务和客户端均能够独立地向对方发送消息。对于必须直接与客户端通信或向消息交换的任意一方提供异步体验（包括类似于事件的行为）的服务来说，这种双向通信形式非常有用

2.若要设计双工协定，还必须设计回调协定，并将该回调协定的类型分配给标记服务协定的ServiceContractAttribute 属性(attribute)的CallbackContract 属性(property)。

3.若要实现双工模式，您必须创建第二个接口，该接口包含服务端在客户端调用的方法声明

eg:

1.在IService1中

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Serialization;
using System.ServiceModel;
using System.Text;

namespace WcfServiceLibrary2
{
    [ServiceContract(Namespace = "http://Microsoft.ServiceModel.Samples", SessionMode = SessionMode.Required,
             CallbackContract = typeof(ICalculatorDuplexCallback))]
    public interface ICalculatorDuplex
    {
        [OperationContract(IsOneWay = true)]
        void Clear();
        [OperationContract(IsOneWay = true)]
        void AddTo(double n);
        [OperationContract(IsOneWay = true)]
        void SubtractFrom(double n);
        [OperationContract(IsOneWay = true)]
        void MultiplyBy(double n);
        [OperationContract(IsOneWay = true)]
        void DivideBy(double n);
    }

    public interface ICalculatorDuplexCallback
    {
        [OperationContract(IsOneWay = true)]
        void Equals(double result);
        [OperationContract(IsOneWay = true)]
        void Equation(string eqn);
    }

}

 CallbackContract = typeof(ICalculatorDuplexCallback))]表示服务端从客户端调用的是ICalculatorDuplexCallback这个接口，这个接口的实现可以在客户端的cs中实现

2.在Service中

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Serialization;
using System.ServiceModel;
using System.Text;

namespace WcfServiceLibrary2
{
    [ServiceBehavior(InstanceContextMode = InstanceContextMode.PerSession)]
    public class CalculatorService : ICalculatorDuplex
    {
        double result;
        string equation;
        ICalculatorDuplexCallback callback = null;

        public CalculatorService()
        {
            result = 0.0D;
            equation = result.ToString();
            callback = OperationContext.Current.GetCallbackChannel<ICalculatorDuplexCallback>();
        }

        public void Clear()
        {
            callback.Equation(equation + " = " + result.ToString());
            result = 0.0D;
            equation = result.ToString();
        }

        public void AddTo(double n)
        {
            result += n;
            equation += " + " + n.ToString();
            callback.Equals(result);
        }

        public void SubtractFrom(double n)
        {
            result -= n;
            equation += " - " + n.ToString();
            callback.Equals(result);
        }

        public void MultiplyBy(double n)
        {
            result *= n;
            equation += " * " + n.ToString();
            callback.Equals(result);
        }

        public void DivideBy(double n)
        {
            result /= n;
            equation += " / " + n.ToString();
            callback.Equals(result);
        }
    }
}

在app中，将binding更改<endpoint address=""  binding="wsDualHttpBinding" contract="WcfServiceLibrary2.ICalculatorDuplex">

3.新建一个窗体应用程序，然后引用这个service，在progrom中

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ServiceModel;
using ConsoleApplication1.ServiceReference1;

namespace ConsoleApplication1
{
    public class CallbackHandler : ICalculatorDuplexCallback
    {
        public void Equals(double result)
        {
            Console.WriteLine("Result({0})", result);
        }

        public void Equation(string eqn)
        {
            Console.WriteLine("Equation({0})", eqn);
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            //指定服务端调用客户端的方法
            InstanceContext instanceContext = new InstanceContext(new CallbackHandler());

            ServiceReference1.CalculatorDuplexClient client = new ServiceReference1.CalculatorDuplexClient(instanceContext);

            //加
            double value = 100.00D;
            client.AddTo(value);

            //减
            value = 50.00D;
            client.SubtractFrom(value);

            //乘
            value = 17.65D;
            client.MultiplyBy(value);

            //除
            value = 2.00D;
            client.DivideBy(value);

            //清除
            client.Clear();

            //关闭
            Console.ReadLine();
            client.Close();
        }
    }
}