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

17 Jun 2020 17:13 #8592 by fbenitez-inblic
Not sure if the previous reply got to you. I am writing it again.

1. Yes I have an entry every time the EasyDAClient tries to Read, Write or subscribe to any item and the application closes/crashes:

Faulting application name: TestWrite.exe, version:, time stamp: 0xfd85b8d1
Faulting module name: ntdll.dll, version: 10.0.19041.207, time stamp: 0x1bdbc4b8
Exception code: 0xc0000374
Fault offset: 0x000e5af3
Faulting process id: 0x282c
Faulting application start time: 0x01d644b3d1736abd
Faulting application path: D:\DevOps\Test Projects\OPCRW\TestWrite-FW47\bin\Debug\TestWrite-FW47.exe
Faulting module path: C:\WINDOWS\SYSTEM32\ntdll.dll
Report Id: 0d2e3aa5-db7b-4741-899a-92707cef4e84
Faulting package full name:
Faulting package-relative application ID:

2. Yes I have two of them:

Also, I have made some additional tests with a third party library I found referenced in the forum: and was able to read / write the same OPC Server as expected under FW 4.7+.

This is the sample code:
using System;
using Hylasoft.Opc.Da;
namespace TestWrite_H_OPC
    class Program
        static void Main(string[] args)
            using (var client = new DaClient(new Uri("opcda://")))
                var tag = "Simulation Examples.Functions.Write1";
                client.Write(tag, 150); // Write Value
                var val = client.Read<o-bject>(tag).Value; // Read Value

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17 Jun 2020 05:33 #8590 by support

Whatever happens when you target .NET Framework 4.6.2 with QuickOPC 2020.2 is undefined by design, because this version of .NET Framework is not supported (see the documentation of that version, or ).

So I believe we can reduce your post to this part: "If the the example is targeting Framework 4.7+ the application closes, no trace at all.".

Can you please check some things:

1. Type "Event Viewer" into the Windows Search box and start the Event Viewer app. In the tree on the left hand side, expand Event Viewer (local) -> Windows Logs and select Application. Inspect the events on the right hand side. Is there any event around the time you started the example?

2. Check the output directory of your project. Do you have .DLL files that whose names start with App_Web... there?

Thank you

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17 Jun 2020 03:49 - 17 Jun 2020 05:26 #8588 by fbenitez-inblic
I am adding the sample code at the end of the explanation.

This error started with Windows 10 Update to Version 2004 OS Build 19041.329

I have tested the following libraries:
Nuget -> 5.58.192
Nuget -> 5.59.0-rev7

If the the example is targeting Framework 4.7+ the application closes, no trace at all.
If the the example is targeting Framework 4.6.2 then, the OpcException is thrown

"The requested OPC Data Access technology 'Com' is not supported. Check the scheme \"opcda\" in server URL string \"opcda:Kepware.KEPServerEX.V6\".\r\n\r\n+ OPC specifications based on COM/DCOM are only supported under .NET Framework.\r\n+ The client method called was 'WriteMultipleItemValues'."

Now here is where it gets even stranger, if i run the Samples from the full installation, the ones that are in Windows Forms they do work.

This is happening completely new projects with zero references to anything else, and I need this EasyDAClient to be created from code behind because it will be running on a windows service.

The OPC is working and I was able to write the Tag in question using the sample application: Demo Application (OPC-DA) and running it from the Visual Studio from the samples.

These was working prior the Windows Update.

This is the simple source code (only 2 lines)
Also, the same issue if the EasyDAClient.SharedInstance is used

The Kepware OPC Server has been uninstalled / reinstalled several times.

Please advice.

This is the sample code
using OpcLabs.EasyOpc.DataAccess;
using OpcLabs.EasyOpc.OperationModel;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace TestWrite
    class Program
        static void Main(string[] args)
            var client = new EasyDAClient();
                client.WriteItemValue("", "Kepware.KEPServerEX.V6", "Simulation Examples.Functions.Write1", "10");
            catch(OpcException e)
                Console.WriteLine("OPC Exception was thrown");
            catch(Exception e)
                Console.WriteLine("Unhandled Exception was thrown");
Last edit: 17 Jun 2020 05:26 by support. Reason: code formatting

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