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"The requested OPC Data Access technology 'Com' is not supported"

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10 Jan 2019 11:07 #6970 by support
You are welcome. I am glad that it works :-)

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09 Jan 2019 22:40 #6969 by jc831
After modifying the project to use 4.6.2, everything seems to be working as expected now. Thanks again for your support.

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08 Jan 2019 23:12 #6961 by jc831
Thank you for that information. I have modified my project to use 4.6.2, but the machine I need to test it on is currently being integrated into a larger piece of equipment so I won't be able to verify for a couple of days. I will post back here when I can confirm it is working.

Thanks again for your support.

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08 Jan 2019 08:47 #6958 by support
If you are targeting .NET Framework, QuickOPC 2018.3 requires version 4.6.2 as minimum. That can be reason for the problems. Switch the target of your project to .NET 4.6.2 first (if you can, start over from scratch, because even the additional references you have added might be thus wrong)

Using the standalone installer is recommended anyway, but not for the reason you gave. OPC-DA (COM-based) *is* supported in the NuGet package. What is not supported in the NuGet package is COM development (as opposed to .NET development) - that means tools like VB6, VBScript, C/C++, PHP, Python, VBA (in Excel), Delphi, PowerBuilder etc. That's not your case, you are doing .NET apparently. So NuGet is OK in general, but NuGet gives you just the assemblies. The standalone installer also has examples, tools etc.

Best regards

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08 Jan 2019 08:30 #6957 by jc831
It is within a .NET Framework 4.6.1 DLL (hosted in a WinForms app). I looked at the link you provided, and I see that COM is not supported via Nuget, but it is supported via the standalone installer. So perhaps the solution is to remove the Nuget package and install the standalone installer?

I'll try that tomorrow if I don't hear from you before then.

Thanks again for your assistance.

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08 Jan 2019 06:52 #6956 by support
Thanks for more information.

Which .NET runtime and version is your project targeting, and what type of project is it (e.g. a class library, console app, Web app, Web service, etc.).

If you are targeting .NET Standard (class library) or .NET Core (app), then the behavior is as expected, because OPC DA (COM-based) is not supported: see opclabs.doc-that.com/files/onlinedocs/QuickOpc/Latest/User%2...l#Development%20Platforms.html

Best regards

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07 Jan 2019 19:59 #6955 by jc831
The snippet shown is exactly what I executed. I have other QuickOPC code in the app (to subscribe to some tags), but those two lines are copied directly from a function that I executed with no other lines in between.

I'm sorry, I'm not at that machine at the moment, but the version should be the latest: I just pulled the Nuget package on Friday morning.

I don't think it is relevant, but just in case, I'll mention that after pulling the QuickOPC Nuget package, the code built but threw an exception at runtime creating the EasyDAClient instance because it couldn't find System.ServiceModel.Primitives.dll. I found that as a separate Nuget package, and after adding that, I could create the EasyDAClient instance. I assume that is as expected.

Thanks for your assistance.

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07 Jan 2019 19:02 #6954 by support
Hello, that's weird - should not normally happen.

Have you set some instance or properties on the EasyDAClient class? In other words, is the snippet about the only part in your test that does something related to QuickOPC, or is there more?

Also, which version are using please?

Best regards

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07 Jan 2019 18:45 #6953 by jc831
Hello,
I am trying to connect to a Kepware OPC server. I am using this snippet:
EasyDAClient client = new EasyDAClient();
            var dav = client.ReadItem("localhost", "Kepware.KEPServerEX.V6", tag);

The ReadItem call throws:

NotSupportedException: The requested OPC Data Access technology 'Com' is not supported. Check the scheme "opcda" in server URL string "opcda://localhost/Kepware.KEPServerEX.V6".
+ The client method called was 'ReadMultipleItems'.


I have tried searching the documentation and this forum for this exception, but I haven't had any luck. Can you suggest what I may have done wrong? The URL shown in the exception is exactly the URL I am using successfully in ClientAce, so I am sure the server is there.

Thanks,
Jeff
 

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