.net - 更新到 .net 4.0 后 wcf 回调异常

Question

我有一个 wcf 服务，它使用 DualHttpBindings 的回调。该服务在找到它们时将搜索结果的数据表推送回客户端(用于长时间运行的搜索)。

这在 .Net 3.5 中运行良好。自从我更新到 .Net 4.0 后，它会以 System.Runtime.FatalException 的形式爆炸，实际上杀死了 IIS 工作进程。我什至不知道如何着手解决这个问题。任何建议表示赞赏。

生成的事件日志中的信息粘贴在下面:

An unhandled exception occurred and the process was terminated.

Application ID: /LM/W3SVC/2/ROOT/CP

Process ID: 5284

> Exception: System.Runtime.FatalException

> Message: Object reference not set to an instance of an object.

StackTrace: at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage4(MessageRpc& rpc) at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage31(MessageRpc& rpc) at System.ServiceModel.Dispatcher.MessageRpc.Process(Boolean isOperationContextSet) at System.ServiceModel.Dispatcher.ChannelHandler.DispatchAndReleasePump(RequestContext request, Boolean cleanThread, OperationContext currentOperationContext) at System.ServiceModel.Dispatcher.ChannelHandler.HandleRequest(RequestContext request, OperationContext currentOperationContext) at System.ServiceModel.Dispatcher.ChannelHandler.AsyncMessagePump(IAsyncResult result) at System.Runtime.Fx.AsyncThunk.UnhandledExceptionFrame(IAsyncResult result) at System.Runtime.AsyncResult.Complete(Boolean completedSynchronously) at System.Runtime.InputQueue1.AsyncQueueReader.Set(Item item) at System.Runtime.InputQueue1.Dispatch() at System.ServiceModel.Channels.ReliableDuplexSessionChannel.ProcessDuplexMessage(WsrmMessageInfo info) at System.ServiceModel.Channels.ReliableDuplexSessionChannel.HandleReceiveComplete(IAsyncResult result) at System.ServiceModel.Channels.ReliableDuplexSessionChannel.OnReceiveCompletedStatic(IAsyncResult result) at System.Runtime.Fx.AsyncThunk.UnhandledExceptionFrame(IAsyncResult result) at System.Runtime.AsyncResult.Complete(Boolean completedSynchronously) at System.ServiceModel.Channels.ReliableChannelBinder1.InputAsyncResult1.OnInputComplete(IAsyncResult result) at System.Runtime.Fx.AsyncThunk.UnhandledExceptionFrame(IAsyncResult result) at System.Runtime.AsyncResult.Complete(Boolean completedSynchronously) at System.Runtime.InputQueue1.AsyncQueueReader.Set(Item item) at System.Runtime.InputQueue1.Dispatch() at System.Runtime.IOThreadScheduler.ScheduledOverlapped.IOCallback(UInt32 errorCode, UInt32 numBytes, NativeOverlapped* nativeOverlapped)
at System.Runtime.Fx.IOCompletionThunk.UnhandledExceptionFrame(UInt32 error, UInt32 bytesRead, NativeOverlapped* nativeOverlapped)
at System.Threading._IOCompletionCallback.PerformIOCompletionCallback(UInt32 errorCode, UInt32 numBytes, NativeOverlapped* pOVERLAP)

> InnerException: > System.NullReferenceException

Message: Object reference not set to an instance of an object.

StackTrace: at System.Web.HttpApplication.ThreadContext.Enter(Boolean setImpersonationContext) at System.Web.HttpApplication.OnThreadEnterPrivate(Boolean setImpersonationContext) at System.Web.AspNetSynchronizationContext.CallCallbackPossiblyUnderLock(SendOrPostCallback callback, Object state) at System.Web.AspNetSynchronizationContext.CallCallback(SendOrPostCallback callback, Object state) at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage4(MessageRpc& rpc)

Answer 1

好的 - 我找到了答案。很奇怪，但只需将以下属性放在 WCF 回调包装器类上:

[CallbackBehavior(UseSynchronizationContext=false)]

感谢 Cauldwell.net 的回答:http://www.cauldwell.net/patrick/blog/CategoryView,category,CodeGen.aspx

来自 cauldwell.net:

The problem, it turned out, was that ASP.NET uses (by default) a little thing called the SynchronizationContext. As near as I can tell (I haven't researched this thoroughly, to be honest) one of it's jobs it to make sure that any callbacks get run on the UI thread, thereby obviating the need to call Control.Invoke like you do in WinForms. In my case, that additional lock was giving something fits, and it was trying to clean stuff up on a thread that wasn't around any more, hence to NullReferenceException.