WCF的回调使用实例代码说明

很多时候我们会遇到,信息及时推送通知的情况，例如：监控设备时及时推送状态、报警信息等,我们就可以用WCF的回调机制来实现,下面以一个监控设备名字为例，如果设备名字发生改变，服务器就马上推送消息给客户端：
（一、）服务器端

1、建一个控制台应用程序：CallbackContractWCF
2、创建ISendMessage接口

namespace CallbackContractWCF
{
    [ServiceContract(CallbackContract = typeof(IMessageCallbackContract))]
   public interface ISendMessage
    {
        /// 
        /// 保存客户端回调的实例
        /// 
        [OperationContract]
        void Subscribe();
    }
}

3、创建用于推送消息回调的接口IMessageCallbackContract

namespace CallbackContractWCF
{
   public interface IMessageCallbackContract
    {
        [OperationContract(IsOneWay = true)]
        void ReportMes(string responseToGreeting);
    }
}

4、创建实现接口ISendMessage的类SendMessage

 1 namespace CallbackContractWCF
 2 {
 3     [ServiceBehavior(InstanceContextMode=InstanceContextMode.Single,ConcurrencyMode=ConcurrencyMode.Multiple,UseSynchronizationContext=false)]
 4     public class SendMessage:ISendMessage
 5     {
 6         private System.Timers.Timer _setValueTimer;
 7         private IMessageCallbackContract callerProxy = null;
 8         ~SendMessage()
 9         {
10             _setValueTimer.Stop();
11             Device.OnChange -= new Action(Student_OnChange);
12         }
13         public SendMessage()
14         {
15             Thread.Sleep(3000);
16             _setValueTimer = new System.Timers.Timer();
17             _setValueTimer.AutoReset = true;
18             _setValueTimer.Elapsed += Timer_Elapsed;
19             _setValueTimer.Interval = 10000;
20             _setValueTimer.Start();
21             Device.OnChange += new Action(Student_OnChange);
22         }
23         //保存客户端回调的实例
24         public void Subscribe()
25         {
26             try
27             {
28                 //获取当前调用的核心服务端实例的通道
29                 callerProxy = OperationContext.Current.GetCallbackChannel();
30             }
31             catch (Exception ex)
32             {
33                 throw new FaultException(ex.Message);
34             }
35         }    
36         private void Timer_Elapsed(object sender, ElapsedEventArgs e)
37         {
38             Random rand = new Random();
39             string name = "路由器"+rand.Next(10);
40             SetName(name);
41         }  
42         private void SetName(string greeting)
43         {
44             if (greeting != Device.Name)
45             {
46                 Device.Name = greeting;
47                 Device.Change(greeting);
48             } 
49         }  
50         void Student_OnChange(string name)
51         {
52             try
53             {
54                 Console.Write("只要名字与当前的不同就向客户端推送通知\r\n");
55                 callerProxy.ReportMes(name);                    
56             }
57             catch (Exception ex)
58             {
59                 Console.Write(ex.Message);
60             }
61         }
62     }
63     //创建设备类
64     public static class Device
65     {
66         public static string Name { get; set; }
67         public static event Action OnChange;
68         public static void Change(string name)
69         {
70             if (OnChange != null)
71             {
72                 OnChange.Invoke(name);
73             }
74         }
75     }
76 }

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