我正在尝试使用AsyncTargetingPack将一些信息异步记录到针对.NET 4.0的MVC 4控制器操作中的SQL Server。我会直接跳到.NET 4.5,但我的应用程序位于Azure和we're still waiting for the update ...
此代码按预期工作(一行写入我的数据库,没有抛出异常):
public class SystemActionLogger : ISystemActionLogger
{
private readonly ActionBlock<Tuple<SystemAction, object>> actionBlock;
public SystemActionLogger(ISystemActionLogEntryRepository repository)
{
actionBlock = new ActionBlock<Tuple<SystemAction, object>>(
entry => TaskEx.Run(async () =>
{
string data = await JsonConvert.SerializeObjectAsync(entry.Item2);
await repository.PersistAsync(new SystemActionLogEntry(entry.Item1, data));
}));
}
public void Log(SystemAction systemAction, object data)
{
actionBlock.Post(new Tuple<SystemAction, object>(systemAction, data));
}
}
此代码抛出NullReferenceException:
public class SystemActionLogger : ISystemActionLogger
{
private readonly ActionBlock<Tuple<SystemAction, object>> actionBlock;
public SystemActionLogger(ISystemActionLogEntryRepository repository)
{
actionBlock = new ActionBlock<Tuple<SystemAction, object>>(async entry =>
{
string data = await JsonConvert.SerializeObjectAsync(entry.Item2);
await repository.PersistAsync(new SystemActionLogEntry(entry.Item1, data));
});
}
public void Log(SystemAction systemAction, object data)
{
actionBlock.Post(new Tuple<SystemAction, object>(systemAction, data));
}
}
NullReferenceException:“对象引用未设置为对象的实例。”
Server stack trace:
at System.Web.ThreadContext.AssociateWithCurrentThread(Boolean setImpersonationContext)
at System.Web.HttpApplication.OnThreadEnterPrivate(Boolean setImpersonationContext)
at System.Web.LegacyAspNetSynchronizationContext.CallCallbackPossiblyUnderLock(SendOrPostCallback callback, Object state)
at System.Web.LegacyAspNetSynchronizationContext.CallCallback(SendOrPostCallback callback, Object state)
at System.Runtime.CompilerServices.TaskAwaiter.<>c__DisplayClassa.<OnCompletedInternal>b__0(Task param0)
Exception rethrown at [0]:
at System.Runtime.CompilerServices.AsyncMethodBuilderCore.<ThrowAsync>b__1(Object state)
at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem()
at System.Threading.ThreadPoolWorkQueue.Dispatch()
我无法查看异常,因为它是所有外部代码。我不明白为什么第二个代码块失败。这是我最初编写的代码。
我做错了什么?
答案 0 :(得分:5)
我只是遇到了一个非常类似的问题(使用日志记录任务时来自AssociateWithCurrentThread的NullReference)。
我遇到的问题是原始操作没有等待日志记录任务的完成,因此当日志完成并尝试重新加入原始线程时,抛出nullReference,因为原始线程已终止。
这是通过确保请求控制器等待日志记录功能来解决的。
答案 1 :(得分:0)
Dataflow仅适用于.NET 4.5。您在.NET 4.0上运行它的事实是不受支持的,这可能是您看到虚假异常的原因。
答案 2 :(得分:-2)
当我的Web服务以异步方式调用另一个WCF服务时,我遇到了.net4.5这个问题。我只是附加了一个短暂的Wait()
因为我不关心响应(遥测事件)。
public static void Event(string key, string message) {
Telemetry.Event(key, message).Wait(100);
}