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Is WriteValue guaranteed to succeed?

28 Sep 2015 14:17 #3577 by support
If there is a problem with writing, either reported by the server or detected by the client, the EasyUAClient.WriteValue should throw an exception (OpcLabs.EasyOpc.UA.OperationModel.UAException, actually).

If you make this call but the value does not change in the server, then I can think of following possible causes:

1) A problem in the server - it does not actually perform the write, but does not return an error to the client,

2) A bug in the client: it receives an error indication from the server, but does not throw the UAException as it should.

3) The UAException is thrown but your program catches it and "swallows" it silently (not likely but still a possibility).

Best regards

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28 Sep 2015 12:25 #3576 by
Hi, I have an problem at a client site that I'm trying to isolate.

I have subscribed to about 30 alias on a KepWareEx server.
I write to on alias with WriteValue("url", "id", object), I will then get a value changed event from the subscription.

But in some very few cases the value is not changed on the server (and I don't get a value changed event, as expected if the value isn't changed).

Is the WriteValue guaranteed to succeed? Or is there some cases where it will fail to update the value in the PLC but not generate an error?

Bard Hustveit

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