SqlDependency 尝试使用 log4net 执行某些操作并无法启动

Question

我们在 .NET Web 应用程序中使用 SqlDependency。间歇性地在生产中，我们在尝试调用 Start 时收到以下错误：

NullReferenceException - Object reference not set to an instance of an object.
Server stack trace: 
   at System.Object.GetType()
   at log4net.Util.ReadOnlyPropertiesDictionary.GetObjectData(SerializationInfo info, StreamingContext context)
   at System.Runtime.Serialization.Formatters.Binary.WriteObjectInfo.InitSerialize(Object obj, ISurrogateSelector surrogateSelector, StreamingContext context, SerObjectInfoInit serObjectInfoInit, IFormatterConverter converter, ObjectWriter objectWriter, SerializationBinder binder)
   at System.Runtime.Serialization.Formatters.Binary.ObjectWriter.Write(WriteObjectInfo objectInfo, NameInfo memberNameInfo, NameInfo typeNameInfo)
   at System.Runtime.Serialization.Formatters.Binary.ObjectWriter.Serialize(Object graph, Header[] inHeaders, __BinaryWriter serWriter, Boolean fCheck)
   at System.Runtime.Serialization.Formatters.Binary.BinaryFormatter.Serialize(Stream serializationStream, Object graph, Header[] headers, Boolean fCheck)
   at System.Runtime.Remoting.Channels.CrossAppDomainSerializer.SerializeMessageParts(ArrayList argsToSerialize)
   at System.Runtime.Remoting.Messaging.SmuggledMethodCallMessage..ctor(IMethodCallMessage mcm)
   at System.Runtime.Remoting.Messaging.SmuggledMethodCallMessage.SmuggleIfPossible(IMessage msg)
   at System.Runtime.Remoting.Channels.CrossAppDomainSink.SyncProcessMessage(IMessage reqMsg)
Exception rethrown at [0]: 
   at System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg)
   at System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type)
   at SqlDependencyProcessDispatcher.StartWithDefault(String connectionString, String& server, DbConnectionPoolIdentity& identity, String& user, String& database, String& service, String appDomainKey, SqlDependencyPerAppDomainDispatcher dispatcher, Boolean& errorOccurred, Boolean& appDomainStart)
   at System.Data.SqlClient.SqlDependency.Start(String connectionString, String queue, Boolean useDefaults)

启动 SqlDependency 的代码很简单：

SqlDependency.Start(ConnectionStringHelper.GetDatabaseConnectionString(), null);

该错误在将 log4net 从 v1 升级到 v2 后首次出现。我们还收到了一个与 SqlDependency 无法找到 log4net DLL 相关的类似错误，我们通过手动将 DLL 复制到 C:\Windows\system32\inetsrv\ 中更正了该错误

SerializationException - Unable to find assembly 'log4net, Version=2.0.8.0, Culture=neutral, PublicKeyToken=669e0ddf0bb1aa2a'.
Server stack trace: 
   at System.Runtime.Serialization.Formatters.Binary.BinaryAssemblyInfo.GetAssembly()
   at System.Runtime.Serialization.Formatters.Binary.ObjectReader.GetType(BinaryAssemblyInfo assemblyInfo, String name)
   at System.Runtime.Serialization.Formatters.Binary.ObjectMap..ctor(String objectName, String[] memberNames, BinaryTypeEnum[] binaryTypeEnumA, Object[] typeInformationA, Int32[] memberAssemIds, ObjectReader objectReader, Int32 objectId, BinaryAssemblyInfo assemblyInfo, SizedArray assemIdToAssemblyTable)
   at System.Runtime.Serialization.Formatters.Binary.__BinaryParser.ReadObjectWithMapTyped(BinaryObjectWithMapTyped record)
   at System.Runtime.Serialization.Formatters.Binary.__BinaryParser.Run()
   at System.Runtime.Serialization.Formatters.Binary.ObjectReader.Deserialize(HeaderHandler handler, __BinaryParser serParser, Boolean fCheck, Boolean isCrossAppDomain, IMethodCallMessage methodCallMessage)
   at System.Runtime.Serialization.Formatters.Binary.BinaryFormatter.Deserialize(Stream serializationStream, HeaderHandler handler, Boolean fCheck, Boolean isCrossAppDomain, IMethodCallMessage methodCallMessage)
   at System.Runtime.Remoting.Channels.CrossAppDomainSerializer.DeserializeObject(MemoryStream stm)
   at System.Runtime.Remoting.Messaging.SmuggledMethodCallMessage.FixupForNewAppDomain()
   at System.Runtime.Remoting.Channels.CrossAppDomainSink.DoDispatch(Byte[] reqStmBuff, SmuggledMethodCallMessage smuggledMcm, SmuggledMethodReturnMessage& smuggledMrm)
   at System.Runtime.Remoting.Channels.CrossAppDomainSink.DoTransitionDispatchCallback(Object[] args)
Exception rethrown at [0]: 
   at System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg)
   at System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type)
   at System._AppDomain.CreateInstance(String assemblyName, String typeName)
   at System.Data.SqlClient.SqlDependency.CreateProcessDispatcher(_AppDomain masterDomain)
   at System.Data.SqlClient.SqlDependency.ObtainProcessDispatcher()
   at System.Data.SqlClient.SqlDependency.Start(String connectionString, String queue, Boolean useDefaults)

为什么 SqlDependency 与 log4net 有任何关系？

Answer 1

我认为还有一个尚未解决的类型导致NullReferenceException - Object reference not set to an instance of an object..

stacktrace 中的最后两条语句表示：

Server stack trace: 
   at System.Object.GetType()
   at log4net.Util.ReadOnlyPropertiesDictionary.GetObjectData(SerializationInfo info, StreamingContext context)

我的猜测是，这log4net也使用外部程序集引用，因此请尝试log4net使用 Fuslogvw.exe 解决它（） - https://learn.microsoft.com/en-us/dotnet/framework/tools/fuslogvw-exe- assembly-binding -日志查看器

如果引用的另一个程序集弹出，C:\Windows\system32\inetsrv\也将其复制到。