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- QuickOPC-Classic in .NET
- Reading, Writing, Subscriptions, Property Access
- Object reference not set to an instance of an object. QuickOPC 2020.3 alpha
Object reference not set to an instance of an object. QuickOPC 2020.3 alpha
Thank you for your assistance,
I'm awaiting approval from the customer to update installation. I'll keep you informed
Regards
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can you please rebuild and test with 5.59.0-rev23 from nuget.org. In relation to this issue, what we are looking for is the call stack again (the innermost exception being the most important; now, there will likely be two of them, the actual exception thrown will be InvalidOperationException ,with inner exception of type NullReferenceException).
Thank you very much for cooperation.
Note that there were some changes; specifically, the EnableNativeClient and EnableNetApiClient properties are now under InstanceParameters and thus need to be set on each new instance of EasyDAClient separately. See kb.opclabs.com/What%27s_new_in_QuickOPC_2020.3 for more information about the changes.
Best regards
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You are right, I need nuget packages
Regards
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You need the NuGet packages and do not need the standalone installer, is that correct?
Regards
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Here are the answers to your questions
1. I don't have a reproducible scenario. Unfortunately, this exception happens on customer site
2. I can't debug the application on the customer site
3. Yes, I can use special build of QuickOpc.
Regards
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the developer was unable to reproduce it, and he was also unable to find the issue by analyzing the code. The problem is that with the way the code is written, the original call stack gets overwritten - it is not the one you could have provided.
Questions:
1. Do you have a reproducible scenario, or hints as to how to "likely" get the error?
2. Can you perhaps reproduce the problem under debugger, with exception settings set so that it breaks the exception when a NullReferenceException is thrown (not just when it is unhandled), and when that happens, capture the call stack for us?
3. If none of the above is possible or gives result, would you be willing to try to reproduce on your side with one more "special" build of QuickOPC, which would have the error handling modified just for this case, to presumably catch the proper information we need (the original call stack etc.)?
Kind regards
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Do you have any updates?
Regards
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I have forwarded the issue to the programmer who worked on this part. Will let you know here when I know more.
Kind regards
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We got an email confirmation from OPC Labs regarding the use of “alpha” version of QuickOPC 2020.3 in test mode to solve the following problem
www.opclabs.com/forum/reading-writing-subscriptions-property...-blocked-subscribe-unsubscribe
Recently, I found a null-reference exception that causes my application to crash. Could you fix that?
QuickOpc version 5.59.0-rev13
EnableNativeClient: False
System.NullReferenceException: Object reference not set to an instance of an object.
at OpcLabs.EasyOpc.Implementation.NetApi.DataAccess.NetApiEasyDAClient.CheckException(Exception exception, Boolean isOtherMethod)
at OpcLabs.EasyOpc.Implementation.NetApi.DataAccess.NetApiSubscription.RemoveItemsFromOneSubscription(NetApiOpcDaSubscription subscription, IList`1 itemsToRemove, Boolean freeHandleForSucceeded, NetApiCacheEventArgs cacheEventsArgs)
at OpcLabs.EasyOpc.Implementation.NetApi.DataAccess.NetApiSubscription.RemoveItems(IList`1 itemsToRemove)
at OpcLabs.EasyOpc.Implementation.NetApi.DataAccess.NetApiSubscription.RemoveItemsL1(IEnumerable`1 handles)
at OpcLabs.EasyOpc.Implementation.NetApi.DataAccess.NetApiSubscription.OnTimer(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.TimerQueueTimer.CallCallback()
at System.Threading.TimerQueueTimer.Fire()
at System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem()
at System.Threading.ThreadPoolWorkQueue.Dispatch()
System.NullReferenceException: Object reference not set to an instance of an object.
at OpcLabs.EasyOpc.Implementation.NetApi.DataAccess.NetApiEasyDAClient.CheckException(Exception exception, Boolean isOtherMethod)
at OpcLabs.EasyOpc.Implementation.NetApi.DataAccess.NetApiSubscription.RemoveItemsFromOneSubscription(NetApiOpcDaSubscription subscription, IList`1 itemsToRemove, Boolean freeHandleForSucceeded, NetApiCacheEventArgs cacheEventsArgs)
at OpcLabs.EasyOpc.Implementation.NetApi.DataAccess.NetApiSubscription.RemoveItems(IList`1 itemsToRemove)
at OpcLabs.EasyOpc.Implementation.NetApi.DataAccess.NetApiSubscription.RemoveItemsL1(IEnumerable`1 handles)
at OpcLabs.EasyOpc.Implementation.NetApi.DataAccess.NetApiSubscription.OnTimer(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.TimerQueueTimer.CallCallback()
at System.Threading.TimerQueueTimer.Fire()
at System.Threading.TimerQueue.FireNextTimers()
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- Forum
- Discussions
- QuickOPC-Classic in .NET
- Reading, Writing, Subscriptions, Property Access
- Object reference not set to an instance of an object. QuickOPC 2020.3 alpha