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Reading/writing

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07 Jun 2024 10:10 #12857 by support
Replied by support on topic Reading/writing
Hello.
as far as I can tell, you are doing it right, and you cannot do more.

In general, the server is entitled to perform the write asynchronously (i.e. after the Write service call returns); in such case it should return an indication of this happening - in QuickOPC this is exposed as .CompletesAsynchronously flag of UAWriteResult-s returned from the WriteMultiple/WriteMultipleValues/WriteList/WriteValueList. But even if the server does indicate this properly, you cannot disable it, at least not in any standard OPC UA way.

Ask the server vendor about this behavior.

Best regards

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06 Jun 2024 16:54 #12856 by spaxman
Reading/writing was created by spaxman
I am using the OpcLabs.EasyOpc.UA.EasyUAClient with these read parameters

opc_struc.item_list[ll_idx] = CREATE OLEObject
opc_struc.item_list[ll_idx].ConnectToNewObject("OpcLabs.EasyOpc.UA.OperationModel.UAReadArguments")
opc_struc.item_list[ll_idx].EndpointDescriptor.UrlString = gs_opc_ua_server
opc_struc.item_list[ll_idx].NodeDescriptor.NodeId.ExpandedText = ls_ns +opc_struc.item_ids[ll_idx]
opc_struc.item_list[ll_idx].ReadParameters.MaximumAge = 0

I issure a write to clear a tag that just containers a number (100) write a value of 0
then I issue a read but sometimes (not always) I get a value of 100 back and not the 0 I just wrote to the tag.

How can I force the write to complete before I read the value.

using WriteValueList for the write and ReadList for the read

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