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06/14/2017
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Hello,
I use some OPC UA dll from the SDK (OPC.Ua.Client.Dll and OPC.Ua.Core.Dll), with KEP Server EX OPC Server in C#.
I need to know first if it is allowed in a Session.Notification handler of a subscription, to write a value to a tag that is monitored by that subscription.
Because, what I tried to do is to delete the subscription before writing that value (beacause I was afraid that the write would generate a notification event again), and, the hmi program still works, but when I do that, opc communication speed appears to be a lot slower.
Regards,
Xavier
05/30/2017
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Why is getting an update after a write a problem?
06/14/2017
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Ok, it’s not a problem, it works.
I thought that it could be a problem, thank you.
I have some other questions regarding the Session.Notification event.
It seams that if an event is not finished, a new event can happen and execute in another thread ?
Can a notification event take for example as much as 200 ms, for example to update HMI graphics or is it a problem ?
05/30/2017
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The Session object is multithreaded. You need to design accordingly.
Note that you generally cannot update UI controls from the callback threads and if you block waiting for access to the UI you could see deadlocks.
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