如何在WCF双工设置中处理客户端上的回调方法中抛出的异常?
目前,客户端似乎没有引发故障事件(除非我不正确地监控它?)但是使用客户端调用Ping()之后的任何事件都失败并显示CommunicationException:“通信对象System.ServiceModel。 Channels.ServiceChannel,因为已被中止而不能用于通信。“。
如何处理此问题并重新创建客户端等?我的第一个问题是如何找出它何时发生。其次,如何最好地处理它?</ p>
我的服务和回调合同:
[ServiceContract(CallbackContract = typeof(ICallback), SessionMode = SessionMode.Required)]
public interface IService
{
[OperationContract]
bool Ping();
}
public interface ICallback
{
[OperationContract(IsOneWay = true)]
void Pong();
}
我的服务器实施:
[ServiceBehavior(InstanceContextMode = InstanceContextMode.PerCall, ConcurrencyMode = ConcurrencyMode.Single)]
public class Service : IService
{
public bool Ping()
{
var remoteMachine = OperationContext.Current.GetCallbackChannel<ICallback>();
remoteMachine.Pong();
}
}
我的客户端实施:
[CallbackBehavior(UseSynchronizationContext = false, ConcurrencyMode = ConcurrencyMode.Single)]
public class Client : ICallback
{
public Client ()
{
var context = new InstanceContext(this);
var proxy = new WcfDuplexProxy<IApplicationService>(context);
(proxy as ICommunicationObject).Faulted += new EventHandler(proxy_Faulted);
//First Ping will call the Pong callback. The exception is thrown
proxy.ServiceChannel.Ping();
//Second Ping call fails as the client is in Aborted state
try
{
proxy.ServiceChannel.Ping();
}
catch (Exception)
{
//CommunicationException here
throw;
}
}
void Pong()
{
throw new Exception();
}
//These event handlers never get called
void proxy_Faulted(object sender, EventArgs e)
{
Console.WriteLine("client faulted proxy_Faulted");
}
}
答案 0 :(得分:1)
事实证明,你不能指望提出Faulted事件。因此,重新建立连接的最佳方法是在后续调用Ping()失败时执行此操作:
我会在这里保持代码简单:
public class Client : ICallback
{
public Client ()
{
var context = new InstanceContext(this);
var proxy = new WcfDuplexProxy<IApplicationService>(context);
(proxy.ServiceChannel as ICommunicationObject).Faulted +=new EventHandler(ServiceChannel_Faulted);
//First Ping will call the Pong callback. The exception is thrown
proxy.ServiceChannel.Ping();
//Second Ping call fails as the client is in Aborted state
try
{
proxy.ServiceChannel.Ping();
}
catch (Exception)
{
//Re-establish the connection and try again
proxy.Abort();
proxy = new WcfDuplexProxy<IApplicationService>(context);
proxy.ServiceChannel.Ping();
}
}
/*
[...The rest of the code is the same...]
//*/
}
显然,在我的示例代码中,Exception将再次抛出,但我希望这对于让人们了解如何重新建立连接非常有用。