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When single item's quality is not good, all of the items become null

support
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18 Dec 2025 07:30 - 18 Dec 2025 07:30 #14505 by support

Replied by support on topic When single item's quality is not good, all of the items become null

Hello.

1. What makes you think that the observed data are not simply what the OPC server sends to the client?

2. Is "vtqResults.Succeeded" true or false for the remaining items?

3. If it is true, what is the QUality of those remaining items? If it is false, what is the error associated with them (for start, ErrorMessageBrief)?

Thank you

Last edit: 18 Dec 2025 07:30 by support.

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sigasec
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17 Dec 2025 23:32 #14504 by sigasec

When single item's quality is not good, all of the items become null was created by sigasec

We use QuickOPC 5.83 with .NET 8. Our app is Windows Service that queries local OPC-DA server with 373 node items every 1000 milliseconds. Normally, everything works just fine, but sometimes one of the node's quality differs from 192 (Good), and in this case all the items values become NULL. The code is below:

Code:

var results = new List<double?>();
var serverDescriptor = new ServerDescriptor(Parameters.OPCServerName);

var newVal = new List<DAItemDescriptor>();
foreach (var tag in Parameters.OPCTagList)
{
    newVal.Add(tag);
}

Stopwatch timer = new Stopwatch();
timer.Start();
_easyDAC.InstanceParameters.Timeouts.ReadItem = 10000;
var readParameters = new DAReadParameters(0); // Taking the measurement of the current time even if it has not changed
DAVtqResult[] vtqResults = _easyDAC.ReadMultipleItems(serverDescriptor, newVal.ToArray(), readParameters);

if (vtqResults.Length > 0)
{
    validMeasumentExist = true;
}
timer.Stop();

if (_isDebug_OPC_Read)
{
    Trace.WriteInfo("Elapsed milliseconds: " + timer.ElapsedMilliseconds.ToString() + ", vtqResults.Length=" + vtqResults.Length, true);
}


for (int i = 0; i < vtqResults.Length; i++)
{
    Debug.Assert(vtqResults[i] != null);

    
    if (vtqResults[i].Succeeded)
    {
        results.Add((vtqResults[i].Vtq.Quality == DAQualities.GoodNonspecific) ? Convert.ToDouble(vtqResults[i].Vtq.Value) : null); 
    }
    else
    {
        Trace.WriteException(new Exception(vtqResults[i].ErrorMessageBrief));
        results.Add(null);
    }
}

return results;

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