QuickOPC User's Guide and Reference
DAVtqResult Class
Members 



OpcLabs.EasyOpcClassic Assembly > OpcLabs.EasyOpc.DataAccess.OperationModel Namespace : DAVtqResult Class
Holds result of an operation in form of a OpcLabs.EasyOpc.DataAccess.DAVtq (value, timestamp, and quality).
Object Model
DAVtqResult ClassExceptionCollection ClassNormalizedExceptionCollection ClassNormalizedException ClassNormalizedException ClassDAVtq Class
Syntax
'Declaration
 

<CLSCompliantAttribute(True)>
<ComDefaultInterfaceAttribute(OpcLabs.EasyOpc.DataAccess.OperationModel.ComTypes._DAVtqResult)>
<ComVisibleAttribute(True)>
<GuidAttribute("6075EE51-ED43-48F6-A61C-B7E814D7C7B0")>
<TypeConverterAttribute(System.ComponentModel.ExpandableObjectConverter)>
<ValueControlAttribute("OpcLabs.BaseLib.Forms.Common.ObjectSerializationControl, OpcLabs.BaseLibForms, Version=5.63.115.1, Culture=neutral, PublicKeyToken=6faddca41dacb409", 
   DefaultReadWrite=False, 
   Export=True, 
   PageId=10001)>
<SerializableAttribute()>
Public Class DAVtqResult 
   Inherits OpcLabs.BaseLib.OperationModel.OperationResult
   Implements LINQPad.ICustomMemberProvider, OpcLabs.BaseLib.ComTypes._Info, OpcLabs.BaseLib.ComTypes._Object2, OpcLabs.BaseLib.OperationModel.ComTypes._OperationResult, OpcLabs.EasyOpc.DataAccess.OperationModel.ComTypes._DAVtqResult, System.ICloneable, System.IFormattable, System.Runtime.Serialization.ISerializable, System.Xml.Serialization.IXmlSerializable 
'Usage
 

Dim instance As DAVtqResult
[CLSCompliant(true)]
[ComDefaultInterface(OpcLabs.EasyOpc.DataAccess.OperationModel.ComTypes._DAVtqResult)]
[ComVisible(true)]
[Guid("6075EE51-ED43-48F6-A61C-B7E814D7C7B0")]
[TypeConverter(System.ComponentModel.ExpandableObjectConverter)]
[ValueControl("OpcLabs.BaseLib.Forms.Common.ObjectSerializationControl, OpcLabs.BaseLibForms, Version=5.63.115.1, Culture=neutral, PublicKeyToken=6faddca41dacb409", 
   DefaultReadWrite=false, 
   Export=true, 
   PageId=10001)]
[Serializable()]
public class DAVtqResult : OpcLabs.BaseLib.OperationModel.OperationResult, LINQPad.ICustomMemberProvider, OpcLabs.BaseLib.ComTypes._Info, OpcLabs.BaseLib.ComTypes._Object2, OpcLabs.BaseLib.OperationModel.ComTypes._OperationResult, OpcLabs.EasyOpc.DataAccess.OperationModel.ComTypes._DAVtqResult, System.ICloneable, System.IFormattable, System.Runtime.Serialization.ISerializable, System.Xml.Serialization.IXmlSerializable  
[CLSCompliant(true)]
[ComDefaultInterface(OpcLabs.EasyOpc.DataAccess.OperationModel.ComTypes._DAVtqResult)]
[ComVisible(true)]
[Guid("6075EE51-ED43-48F6-A61C-B7E814D7C7B0")]
[TypeConverter(System.ComponentModel.ExpandableObjectConverter)]
[ValueControl("OpcLabs.BaseLib.Forms.Common.ObjectSerializationControl, OpcLabs.BaseLibForms, Version=5.63.115.1, Culture=neutral, PublicKeyToken=6faddca41dacb409", 
   DefaultReadWrite=false, 
   Export=true, 
   PageId=10001)]
[Serializable()]
public ref class DAVtqResult : public OpcLabs.BaseLib.OperationModel.OperationResult, LINQPad.ICustomMemberProvider, OpcLabs.BaseLib.ComTypes._Info, OpcLabs.BaseLib.ComTypes._Object2, OpcLabs.BaseLib.OperationModel.ComTypes._OperationResult, OpcLabs.EasyOpc.DataAccess.OperationModel.ComTypes._DAVtqResult, System.ICloneable, System.IFormattable, System.Runtime.Serialization.ISerializable, System.Xml.Serialization.IXmlSerializable
Remarks

The result is successful if the OpcLabs.BaseLib.OperationModel.OperationResult.Exception is a null reference. Otherwise, this property contains information about the reason of the failure.

 

In This Topic

In OPC Data Access, reading data from OPC items is one of the most common tasks. The OPC server generally provides current data for any OPC item in form of a Value, Timestamp and Quality combination (VTQ).

A single item

If you want to read the current VTQ from a specific OPC item, call the ReadItem method. You pass in individual arguments for machine name, server class, ItemID, and an optional data type. You will receive back a DAVtq object holding the current value, timestamp, and quality of the OPC item. The ReadItem method returns the current VTQ, regardless of the quality. You may receive an Uncertain or even Bad quality (and no usable data value), and your code needs to deal with such situations accordingly.

// This example shows how to read a single item, and display its value, timestamp and quality.

using System;
using OpcLabs.EasyOpc.DataAccess;
using OpcLabs.EasyOpc.OperationModel;

namespace DocExamples.DataAccess._EasyDAClient
{
    partial class ReadItem
    {
        public static void Main1()
        {
            // Instantiate the client object.
            var client = new EasyDAClient();

            DAVtq vtq;
            try
            {
                vtq = client.ReadItem("", "OPCLabs.KitServer.2", "Simulation.Random");
            }
            catch (OpcException opcException)
            {
                Console.WriteLine("*** Failure: {0}", opcException.GetBaseException().Message);
                return;
            }

            Console.WriteLine("Vtq: {0}", vtq);
        }
    }
}

# This example shows how to read a single item, and display its value, timestamp and quality.

#requires -Version 5.1
using namespace OpcLabs.EasyOpc.DataAccess
using namespace OpcLabs.EasyOpc.OperationModel

# The path below assumes that the current directory is [ProductDir]/Examples-NET/PowerShell/Windows .
Add-Type -Path "../../../Assemblies/net47/OpcLabs.EasyOpcClassic.dll"

# Instantiate the client object.
$client = New-Object EasyDAClient

try {
    $vtq = [IEasyDAClientExtension]::ReadItem($client, "", "OPCLabs.KitServer.2", "Simulation.Random")
}
catch [OpcException] {
    Write-Host "*** Failure: $($PSItem.Exception.GetBaseException().Message)"
    return
}

Write-Host "Vtq: $($vtq)"

// This example shows how to read a single item, and display its value, timestamp and quality.

$Client = new COM("OpcLabs.EasyOpc.DataAccess.EasyDAClient");

try
{
    $Vtq = $Client->ReadItem("", "OPCLabs.KitServer.2", "Simulation.Random");
}
catch (com_exception $e)
{
    printf("*** Failure: %s\n", $e->getMessage());
    Exit();
}

printf("Vtq: %s\n", $Vtq);

' This example shows how to read a single item, and display its value, timestamp and quality.

Imports OpcLabs.EasyOpc.DataAccess
Imports OpcLabs.EasyOpc.OperationModel

Namespace DocExamples.DataAccess._EasyDAClient
    Partial Friend Class ReadItem
        Public Shared Sub Main1()
            Dim client = New EasyDAClient()

            Dim vtq As DAVtq
            Try
                vtq = client.ReadItem("", "OPCLabs.KitServer.2", "Simulation.Random")
            Catch opcException As OpcException
                Console.WriteLine("*** Failure: {0}", opcException.GetBaseException().Message)
                Exit Sub
            End Try

            Console.WriteLine("Vtq: {0}", vtq)
        End Sub
    End Class
End Namespace

// This example shows how to read a single item, and display its value, timestamp and quality.

var Client = new ActiveXObject("OpcLabs.EasyOpc.DataAccess.EasyDAClient");
var VTQ = Client.ReadItem("", "OPCLabs.KitServer.2", "Simulation.Random");
WScript.Echo("VTQ.ToString(): " + VTQ.ToString());

// This example shows how to read a single item, and display its value, timestamp and quality.

class procedure ReadItem.Main;
var
  Client: OpcLabs_EasyOpcClassic_TLB._EasyDAClient;
  Vtq: _DAVtq;
begin
  // Instantiate the client object
  Client := CoEasyDAClient.Create;

  try
    Vtq := Client.ReadItem('', 'OPCLabs.KitServer.2', 'Simulation.Random');
  except
    on E: EOleException do
    begin
      WriteLn(Format('*** Failure: %s', [E.GetBaseException.Message]));
      Exit;
    end;
  end;

  // Display results
  WriteLn('Vtq: ', Vtq.ToString);
end;

// This example shows how to read a single item, and display its value, timestamp and quality.

mle_outputtext.Text = ""

// Instantiate the client object
OLEObject client
client = CREATE OLEObject
client.ConnectToNewObject("OpcLabs.EasyOpc.DataAccess.EasyDAClient")

// Obtain value/timestamp/quality
OLEObject vtq
TRY
    vtq = client.ReadItem("", "OPCLabs.KitServer.2", "Demo.Ramp")
CATCH (OLERuntimeError oleRuntimeError)
    mle_outputtext.Text = mle_outputtext.Text + "*** Failure: " + oleRuntimeError.Description + "~r~n"
    RETURN
END TRY

// Display results
mle_outputtext.Text = mle_outputtext.Text + "Vtq: " + vtq.DisplayString + "~r~n"

Rem This example shows how to read a single item, and display its value, timestamp and quality.

Private Sub ReadItem_Main_Command_Click()
    OutputText = ""
    
    ' Instantiate the client object
    Dim client As New EasyDAClient

    On Error Resume Next
    Dim vtq As DAVtq
    Set vtq = client.ReadItem("", "OPCLabs.KitServer.2", "Simulation.Random")
    If Err.Number <> 0 Then
        OutputText = OutputText & "*** Failure: " & Err.Source & ": " & Err.Description & vbCrLf
        Exit Sub
    End If
    On Error GoTo 0

    ' Display results
    OutputText = OutputText & "Vtq: " & vtq & vbCrLf
End Sub

Rem This example shows how to read a single item, and display its value, timestamp and quality.

Option Explicit

Dim Client: Set Client = CreateObject("OpcLabs.EasyOpc.DataAccess.EasyDAClient")
On Error Resume Next
Dim Vtq: Set Vtq = Client.ReadItem("", "OPCLabs.KitServer.2", "Simulation.Random")
If Err.Number <> 0 Then
    WScript.Echo "*** Failure: " & Err.Source & ": " & Err.Description
    WScript.Quit
End If
On Error Goto 0
WScript.Echo "Vtq: " & Vtq

In QuickOPC.NET, you can also pass ServerDescriptor and DAItemDescriptor objects in place of individual arguments to the ReadItem method.

// This example shows how to read a single item using a browse path, and display its value, timestamp and quality.

using System;
using OpcLabs.EasyOpc;
using OpcLabs.EasyOpc.DataAccess;
using OpcLabs.EasyOpc.OperationModel;

namespace DocExamples.DataAccess._EasyDAClient
{
    partial class ReadItem
    {
        public static void BrowsePath()
        {
            // Instantiate the client object.
            var client = new EasyDAClient();

            DAVtq vtq;
            try
            {
                vtq = client.ReadItem(
                    new ServerDescriptor("", "OPCLabs.KitServer.2"),
                    new DAItemDescriptor(null, "/Simulation/Random"));
            }
            catch (OpcException opcException)
            {
                Console.WriteLine("*** Failure: {0}", opcException.GetBaseException().Message);
                return;
            }

            Console.WriteLine("Vtq: {0}", vtq);
        }
    }
}

' This example shows how to read a single item using a browse path, and display its value, timestamp and quality.

Imports OpcLabs.EasyOpc
Imports OpcLabs.EasyOpc.DataAccess
Imports OpcLabs.EasyOpc.OperationModel

Namespace DocExamples.DataAccess._EasyDAClient
    Partial Friend Class ReadItem
        Public Shared Sub BrowsePath()
            Dim client = New EasyDAClient()

            Dim vtq As DAVtq
            Try
                vtq = client.ReadItem(New ServerDescriptor("", "OPCLabs.KitServer.2"), New DAItemDescriptor(Nothing, "/Simulation/Random"))
            Catch opcException As OpcException
                Console.WriteLine("*** Failure: {0}", opcException.GetBaseException().Message)
                Exit Sub
            End Try

            Console.WriteLine("Vtq: {0}", vtq)
        End Sub
    End Class
End Namespace

 

Multiple items

For reading VTQs of multiple items simultaneously in an efficient manner, call the ReadMultipleItems method (instead of multiple ReadItem calls in a loop). You will receive back an array of DAVtqResult objects.

In QuickOPC.NET, you can pass in a ServerDescriptor object and an array of DAItemDescriptor objects, or an array of DAItemArguments objects, to the ReadMultipleItems method.

Example 1

// This example shows how to read 4 items at once, and display their values, timestamps and qualities.

using System;
using System.Diagnostics;
using OpcLabs.EasyOpc.DataAccess;
using OpcLabs.EasyOpc.DataAccess.OperationModel;

namespace DocExamples.DataAccess._EasyDAClient
{
    partial class ReadMultipleItems
    {
        public static void Main1()
        {
            // Instantiate the client object.
            var client = new EasyDAClient();

            DAVtqResult[] vtqResults = client.ReadMultipleItems("OPCLabs.KitServer.2",
                new DAItemDescriptor[]
                    {
                        "Simulation.Random", "Trends.Ramp (1 min)", "Trends.Sine (1 min)", "Simulation.Register_I4"
                    });

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

                if (vtqResults[i].Succeeded)
                    Console.WriteLine("vtqResults[{0}].Vtq: {1}", i, vtqResults[i].Vtq);
                else
                    Console.WriteLine("vtqResults[{0}] *** Failure: {1}", i, vtqResults[i].ErrorMessageBrief);
            }
        }
    }
}

# This example shows how to read 4 items at once, and display their values, timestamps and qualities.

#requires -Version 5.1
using namespace OpcLabs.EasyOpc.DataAccess

# The path below assumes that the current directory is [ProductDir]/Examples-NET/PowerShell/Windows .
Add-Type -Path "../../../Assemblies/net47/OpcLabs.EasyOpcClassic.dll"

# Instantiate the client object.
$client = New-Object EasyDAClient

$vtqResults = [IEasyDAClientExtension]::ReadMultipleItems($client, "OPCLabs.KitServer.2", @(
    (New-Object DAItemDescriptor("Simulation.Random")),
    (New-Object DAItemDescriptor("Trends.Ramp (1 min)")),
    (New-Object DAItemDescriptor("Trends.Sine (1 min)")),
    (New-Object DAItemDescriptor("Simulation.Register_I4"))
    ))

for ($i = 0; $i -lt $vtqResults.Length; $i++) {
    $vtqResult = $vtqResults[$i]
    if ($vtqResult.Succeeded) {
        Write-Host "vtqResults[$($i)].Vtq: $($vtqResult.Vtq)"
    }
    else {
        Write-Host "vtqResults[$($i)] *** Failure: $($vtqResult.ErrorMessageBrief)"
    }
}

// This example shows how to read 4 items at once, and display their values, timestamps and qualities.

$ReadItemArguments1 = new COM("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments");
$ReadItemArguments1->ServerDescriptor->ServerClass = "OPCLabs.KitServer.2";
$ReadItemArguments1->ItemDescriptor->ItemID = "Simulation.Random";

$ReadItemArguments2 = new COM("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments");
$ReadItemArguments2->ServerDescriptor->ServerClass = "OPCLabs.KitServer.2";
$ReadItemArguments2->ItemDescriptor->ItemID = "Trends.Ramp (1 min)";

$ReadItemArguments3 = new COM("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments");
$ReadItemArguments3->ServerDescriptor->ServerClass = "OPCLabs.KitServer.2";
$ReadItemArguments3->ItemDescriptor->ItemID = "Trends.Sine (1 min)";

$ReadItemArguments4 = new COM("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments");
$ReadItemArguments4->ServerDescriptor->ServerClass = "OPCLabs.KitServer.2";
$ReadItemArguments4->ItemDescriptor->ItemID = "Simulation.Register_I4";

$arguments[0] = $ReadItemArguments1;
$arguments[1] = $ReadItemArguments2;
$arguments[2] = $ReadItemArguments3;
$arguments[3] = $ReadItemArguments4;

$Client = new COM("OpcLabs.EasyOpc.DataAccess.EasyDAClient");

$results = $Client->ReadMultipleItems($arguments);

for ($i = 0; $i < count($results); $i++)
{
    $VtqResult = $results[$i];
    if ($VtqResult->Succeeded)
        printf("results[d].Vtq.ToString()s\n", $i, $VtqResult->Vtq->ToString);
    else
        printf("results[d]: *** Failures\n", $i, $VtqResult->ErrorMessageBrief);
}

' This example shows how to read 4 items at once, and display their values, timestamps and qualities.

Imports OpcLabs.EasyOpc.DataAccess
Imports OpcLabs.EasyOpc.DataAccess.OperationModel

Namespace DocExamples.DataAccess._EasyDAClient
    Partial Friend Class ReadMultipleItems
        Public Shared Sub Main1()
            Dim client = New EasyDAClient()

            Dim vtqResults() As DAVtqResult = client.ReadMultipleItems(
                "OPCLabs.KitServer.2",
                New DAItemDescriptor() {"Simulation.Random", "Trends.Ramp (1 min)", "Trends.Sine (1 min)", "Simulation.Register_I4"})

            For i = 0 To vtqResults.Length - 1
                Debug.Assert(vtqResults(i) IsNot Nothing)

                If vtqResults(i).Succeeded Then
                    Console.WriteLine("vtqResult[{0}].Vtq: {1}", i, vtqResults(i).Vtq)
                Else
                    Console.WriteLine("vtqResult[{0}] *** Failure: {1}", i, vtqResults(i).ErrorMessageBrief)
                End If
            Next i
        End Sub
    End Class
End Namespace

// This example shows how to read 4 items at once, and display their values, timestamps and qualities.

class procedure ReadMultipleItems.Main;
var
  Arguments: OleVariant;
  Client: OpcLabs_EasyOpcClassic_TLB._EasyDAClient;
  I: Cardinal;
  ReadItemArguments1: _DAReadItemArguments;
  ReadItemArguments2: _DAReadItemArguments;
  ReadItemArguments3: _DAReadItemArguments;
  ReadItemArguments4: _DAReadItemArguments;
  VtqResult: _DAVtqResult;
  Results: OleVariant;
begin
  ReadItemArguments1 := CoDAReadItemArguments.Create;
  ReadItemArguments1.ServerDescriptor.ServerClass := 'OPCLabs.KitServer.2';
  ReadItemArguments1.ItemDescriptor.ItemID := 'Simulation.Random';

  ReadItemArguments2 := CoDAReadItemArguments.Create;
  ReadItemArguments2.ServerDescriptor.ServerClass := 'OPCLabs.KitServer.2';
  ReadItemArguments2.ItemDescriptor.ItemID := 'Trends.Ramp (1 min)';

  ReadItemArguments3 := CoDAReadItemArguments.Create;
  ReadItemArguments3.ServerDescriptor.ServerClass := 'OPCLabs.KitServer.2';
  ReadItemArguments3.ItemDescriptor.ItemID := 'Trends.Sine (1 min)';

  ReadItemArguments4 := CoDAReadItemArguments.Create;
  ReadItemArguments4.ServerDescriptor.ServerClass := 'OPCLabs.KitServer.2';
  ReadItemArguments4.ItemDescriptor.ItemID := 'Simulation.Register_I4';

  Arguments := VarArrayCreate([0, 3], varVariant);
  Arguments[0] := ReadItemArguments1;
  Arguments[1] := ReadItemArguments2;
  Arguments[2] := ReadItemArguments3;
  Arguments[3] := ReadItemArguments4;

  // Instantiate the client object
  Client := CoEasyDAClient.Create;

  TVarData(Results).VType := varArray or varVariant;
  TVarData(Results).VArray := PVarArray(
    Client.ReadMultipleItems(Arguments));

  // Display results
  for I := VarArrayLowBound(Results, 1) to VarArrayHighBound(Results, 1) do
  begin
      VtqResult := IInterface(Results[I]) as _DAVtqResult;
      if VtqResult.Succeeded then
        WriteLn('results(', i, ').Vtq.ToString(): ', VtqResult.Vtq.ToString)
      else
        WriteLn('results(', i, ') *** Failure: ', VtqResult.ErrorMessageBrief);
  end;

  VarClear(Results);
  VarClear(Arguments);
end;

// This example shows how to read 4 items at once, and display their values, timestamps and qualities.

mle_outputtext.Text = ""

// Instantiate the client object
OLEObject client
client = CREATE OLEObject
client.ConnectToNewObject("OpcLabs.EasyOpc.DataAccess.EasyDAClient")

// Prepare arguments.

OLEObject readItemArguments1
readItemArguments1 = CREATE OLEObject
readItemArguments1.ConnectToNewObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")
readItemArguments1.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
readItemArguments1.ItemDescriptor.ItemID = "Simulation.Random"

OLEObject readItemArguments2
readItemArguments2 = CREATE OLEObject
readItemArguments2.ConnectToNewObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")
readItemArguments2.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
readItemArguments2.ItemDescriptor.ItemID = "Trends.Ramp (1 min)"

OLEObject readItemArguments3
readItemArguments3 = CREATE OLEObject
readItemArguments3.ConnectToNewObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")
readItemArguments3.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
readItemArguments3.ItemDescriptor.ItemID = "Trends.Sine (1 min)"

OLEObject readItemArguments4
readItemArguments4 = CREATE OLEObject
readItemArguments4.ConnectToNewObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")
readItemArguments4.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
readItemArguments4.ItemDescriptor.ItemID = "Simulation.Register_I4"

OLEObject readItemArgumentsList
readItemArgumentsList = CREATE OLEObject
readItemArgumentsList.ConnectToNewObject("OpcLabs.BaseLib.Collections.ElasticVector")
readItemArgumentsList.Add(readItemArguments1)
readItemArgumentsList.Add(readItemArguments2)
readItemArgumentsList.Add(readItemArguments3)
readItemArgumentsList.Add(readItemArguments4)

// Obtain values/timestamps/qualities.
OLEObject vtqResultList
vtqResultList = client.ReadItemList(readItemArgumentsList)

// Display results
Int i
FOR i = 0 TO vtqResultList.Count - 1
    OLEObject vtqResult
    vtqResult = vtqResultList.Item[i]
    IF vtqResult.Succeeded THEN
        mle_outputtext.Text = mle_outputtext.Text + "vtqResult[" + String(i) + "].Vtq: " + String(vtqResult.Vtq) + "~r~n"
    ELSE
        mle_outputtext.Text = mle_outputtext.Text + "vtqResult[" + String(i) + "] *** Failure: " + vtqResult.ErrorMessageBrief + "~r~n"
    END IF    
NEXT

Rem $Header: $ Rem This example shows how to read 4 items at once, and display their values, timestamps and qualities.

Dim ReadItemArguments1 As New OLEObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")
ReadItemArguments1.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
ReadItemArguments1.ItemDescriptor.ItemID = "Simulation.Random"

Dim ReadItemArguments2 As New OLEObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")
ReadItemArguments2.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
ReadItemArguments2.ItemDescriptor.ItemID = "Trends.Ramp (1 min)"

Dim ReadItemArguments3 As New OLEObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")
ReadItemArguments3.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
ReadItemArguments3.ItemDescriptor.ItemID = "Trends.Sine (1 min)"

Dim ReadItemArguments4 As New OLEObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")
ReadItemArguments4.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
ReadItemArguments4.ItemDescriptor.ItemID = "Simulation.Register_I4"

Dim argumentsList As New OLEObject("OpcLabs.BaseLib.Collections.ElasticVector")
argumentsList.Add(ReadItemArguments1)
argumentsList.Add(ReadItemArguments2)
argumentsList.Add(ReadItemArguments3)
argumentsList.Add(ReadItemArguments4)

'Dim arguments(3) As OLEObject
'arguments(0) = ReadItemArguments1
'arguments(1) = ReadItemArguments2
'arguments(2) = ReadItemArguments3
'arguments(3) = ReadItemArguments4

Dim Client As New OLEObject("OpcLabs.EasyOpc.DataAccess.EasyDAClient")

Dim resultList As OLEObject
resultList = Client.ReadItemList(argumentsList)
Dim n As Integer
n = resultList.Count

'Dim results() As Variant
'results = Client.ReadMultipleItems(arguments)

Dim i As Integer
For i = 0 To n - 1
  'For i = results.FirstRowIndex To results.LastRowIndex
  Dim VtqResult As OLEObject
  VtqResult = resultList.GetAt(i)
  'VtqResult = results(i)
  If VtqResult.Succeeded Then
    Dim Vtq As OLEObject
    Vtq = VtqResult.Vtq
    Print "results(" + CStr(i) + ").Vtq.ToString(): " + Vtq.ToString()
  Else
    Print "results(" + CStr(i) + ") *** Failure: " + VtqResult.ErrorMessageBrief
  End If
Next

Rem This example shows how to read 4 items at once, and display their values, timestamps and qualities.

Private Sub ReadMultipleItems_Main_Command_Click()
    OutputText = ""
    
    Dim readArguments1 As New DAReadItemArguments
    readArguments1.serverDescriptor.ServerClass = "OPCLabs.KitServer.2"
    readArguments1.ItemDescriptor.itemId = "Simulation.Random"
    
    Dim readArguments2 As New DAReadItemArguments
    readArguments2.serverDescriptor.ServerClass = "OPCLabs.KitServer.2"
    readArguments2.ItemDescriptor.itemId = "Trends.Ramp (1 min)"
    
    Dim readArguments3 As New DAReadItemArguments
    readArguments3.serverDescriptor.ServerClass = "OPCLabs.KitServer.2"
    readArguments3.ItemDescriptor.itemId = "Trends.Sine (1 min)"
    
    Dim readArguments4 As New DAReadItemArguments
    readArguments4.serverDescriptor.ServerClass = "OPCLabs.KitServer.2"
    readArguments4.ItemDescriptor.itemId = "Simulation.Register_I4"
    
    Dim arguments(3) As Variant
    Set arguments(0) = readArguments1
    Set arguments(1) = readArguments2
    Set arguments(2) = readArguments3
    Set arguments(3) = readArguments4

    ' Instantiate the client object
    Dim client As New EasyDAClient

    Dim results() As Variant
    results = client.ReadMultipleItems(arguments)

    ' Display results
    Dim i: For i = LBound(results) To UBound(results)
        Dim vtqResult As DAVtqResult: Set vtqResult = results(i)
        If vtqResult.Succeeded Then
            OutputText = OutputText & "results(" & i & ").Vtq: " & vtqResult.vtq & vbCrLf
        Else
            OutputText = OutputText & "results(" & i & ") *** Failure: " & vtqResult.ErrorMessageBrief & vbCrLf
        End If
    Next
End Sub

Rem This example shows how to read 4 items at once, and display their values, timestamps and qualities.

Option Explicit

Dim ReadItemArguments1: Set ReadItemArguments1 = CreateObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")
ReadItemArguments1.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
ReadItemArguments1.ItemDescriptor.ItemID = "Simulation.Random"

Dim ReadItemArguments2: Set ReadItemArguments2 = CreateObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")
ReadItemArguments2.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
ReadItemArguments2.ItemDescriptor.ItemID = "Trends.Ramp (1 min)"

Dim ReadItemArguments3: Set ReadItemArguments3 = CreateObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")
ReadItemArguments3.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
ReadItemArguments3.ItemDescriptor.ItemID = "Trends.Sine (1 min)"

Dim ReadItemArguments4: Set ReadItemArguments4 = CreateObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")
ReadItemArguments4.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
ReadItemArguments4.ItemDescriptor.ItemID = "Simulation.Register_I4"

Dim arguments(3)
Set arguments(0) = ReadItemArguments1
Set arguments(1) = ReadItemArguments2
Set arguments(2) = ReadItemArguments3
Set arguments(3) = ReadItemArguments4

Dim Client: Set Client = CreateObject("OpcLabs.EasyOpc.DataAccess.EasyDAClient")
Dim results: results = Client.ReadMultipleItems(arguments)

Dim i: For i = LBound(results) To UBound(results)
    Dim VtqResult: Set VtqResult = results(i)
    If VtqResult.Succeeded Then
        WScript.Echo "results(" & i & ").Vtq.ToString(): " & VtqResult.Vtq.ToString()
    Else
        WScript.Echo "results(" & i & ") *** Failure: " & VtqResult.ErrorMessageBrief
    End If
Next

Example 2

// This example repeatedly reads a large number of items.

using System;
using OpcLabs.EasyOpc.DataAccess;
using OpcLabs.EasyOpc.DataAccess.OperationModel;

namespace DocExamples.DataAccess._EasyDAClient
{
    partial class ReadMultipleItems
    {
        private const int RepeatCount = 10;
        private const int NumberOfItems = 1000;

        public static void ManyRepeat()
        {
            Console.WriteLine("Creating array of arguments...");
            var arguments = new DAReadItemArguments[NumberOfItems];
            for (int i = 0; i < NumberOfItems; i++)
            {
                int copy = (i / 100) + 1;
                int phase = i % 100;
                string itemId = FormattableString.Invariant($"Simulation.Incrementing.Copy_{copy}.Phase_{phase}");
                Console.WriteLine(itemId);

                var readItemArguments = new DAReadItemArguments("OPCLabs.KitServer.2", itemId);
                arguments[i] = readItemArguments;
            }

            // Instantiate the client object.
            var client = new EasyDAClient();

            for (int iRepeat = 1; iRepeat <= RepeatCount; iRepeat++)
            {
                Console.WriteLine("Reading items...");
                DAVtqResult[] vtqResults = client.ReadMultipleItems(arguments);

                int successCount = 0;
                foreach (DAVtqResult vtqResult in vtqResults)
                    if (vtqResult.Succeeded)
                        successCount++;
                Console.WriteLine($"Success count: {successCount}");
            }
        }
    }
}

Rem This example repeatedly reads a large number of items.

Option Explicit

Const repeatCount = 10
Const numberOfItems = 1000

WScript.Echo "Creating array of arguments..."
Dim arguments(): ReDim arguments(numberOfItems - 1)
Dim i: For i = 0 To numberOfItems - 1
    Dim copy: copy = Int(i / 100) + 1
    Dim phase: phase = i Mod 100
    Dim itemId: itemId = "Simulation.Incrementing.Copy_" & copy & ".Phase_" & phase
    WScript.Echo itemId

    Dim ReadItemArguments: Set ReadItemArguments = CreateObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")
    ReadItemArguments.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
    ReadItemArguments.ItemDescriptor.ItemID = itemId

    Set arguments(i) = ReadItemArguments
Next

Dim Client: Set Client = CreateObject("OpcLabs.EasyOpc.DataAccess.EasyDAClient")

Dim iRepeat: For iRepeat = 1 To repeatCount
    WScript.Echo "Reading items..."
    Dim results: results = Client.ReadMultipleItems(arguments)

    Dim successCount: successCount = 0
    For i = LBound(results) To UBound(results)
        Dim VtqResult: Set VtqResult = results(i)
        If VtqResult.Succeeded Then successCount = successCount + 1
    Next
    WScript.Echo "Success count: " & successCount
Next

Example 3

// This example shows how to read 4 items at once synchronously, and display their values, timestamps and qualities.

using System;
using System.Diagnostics;
using OpcLabs.EasyOpc.DataAccess;
using OpcLabs.EasyOpc.DataAccess.OperationModel;

namespace DocExamples.DataAccess._EasyDAClient
{
    partial class ReadMultipleItems
    {
        public static void Synchronous()
        {
            // Instantiate the client object.
            var client = new EasyDAClient();

            // Specify that only synchronous method is allowed. By default, both synchronous and asynchronous methods are
            // allowed, and the component picks a suitable method automatically. Disallowing asynchronous method leaves
            // only the synchronous method available for selection.
            client.InstanceParameters.Mode.AllowAsynchronousMethod = false;

            DAVtqResult[] vtqResults = client.ReadMultipleItems("OPCLabs.KitServer.2",
                new DAItemDescriptor[]
                    {
                        "Simulation.Random", "Trends.Ramp (1 min)", "Trends.Sine (1 min)", "Simulation.Register_I4"
                    });

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

                if (vtqResults[i].Succeeded)
                    Console.WriteLine("vtqResult[{0}].Vtq: {1}", i, vtqResults[i].Vtq);
                else
                    Console.WriteLine("vtqResult[{0}] *** Failure: {1}", i, vtqResults[i].ErrorMessageBrief);
            }
        }

        
        // Example output:
        //
        //vtqResult[0].Vtq: 0.00125125888851588 { System.Double} @2020-04-10T15:29:20.642; GoodNonspecific(192)
        //vtqResult[1].Vtq: 0.344052940607071 {System.Double} @2020-04-10T15:29:20.643; GoodNonspecific(192)
        //vtqResult[2].Vtq: 0.830410616568378 {System.Double} @2020-04-10T15:29:20.643; GoodNonspecific(192)
        //vtqResult[3].Vtq: 0 {System.Int32} @1601-01-01T00:00:00.000; GoodNonspecific(192)
    }
}

Rem This example shows how to read 4 items at once synchronously, and display their values, timestamps and qualities.

Option Explicit

Dim ReadItemArguments1: Set ReadItemArguments1 = CreateObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")
ReadItemArguments1.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
ReadItemArguments1.ItemDescriptor.ItemID = "Simulation.Random"

Dim ReadItemArguments2: Set ReadItemArguments2 = CreateObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")
ReadItemArguments2.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
ReadItemArguments2.ItemDescriptor.ItemID = "Trends.Ramp (1 min)"

Dim ReadItemArguments3: Set ReadItemArguments3 = CreateObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")
ReadItemArguments3.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
ReadItemArguments3.ItemDescriptor.ItemID = "Trends.Sine (1 min)"

Dim ReadItemArguments4: Set ReadItemArguments4 = CreateObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")
ReadItemArguments4.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
ReadItemArguments4.ItemDescriptor.ItemID = "Simulation.Register_I4"

Dim arguments(3)
Set arguments(0) = ReadItemArguments1
Set arguments(1) = ReadItemArguments2
Set arguments(2) = ReadItemArguments3
Set arguments(3) = ReadItemArguments4

Dim Client: Set Client = CreateObject("OpcLabs.EasyOpc.DataAccess.EasyDAClient")

' Specify that only synchronous method is allowed. By default, both synchronous and asynchronous methods are allowed, and 
' the component picks a suitable method automatically. Disallowing asynchronous method leaves only the synchronous method
' available for selection.
Client.InstanceParameters.Mode.AllowAsynchronousMethod = False

Dim results: results = Client.ReadMultipleItems(arguments)

Dim i: For i = LBound(results) To UBound(results)
    Dim VtqResult: Set VtqResult = results(i)
    If VtqResult.Succeeded Then
        WScript.Echo "results(" & i & ").Vtq.ToString(): " & VtqResult.Vtq.ToString()
    Else
        WScript.Echo "results(" & i & ") *** Failure: " & VtqResult.ErrorMessageBrief
    End If
Next

Example 4

Rem This example shows how to read 2 items (first valid, second invalid), test for success of each read and display either 
Rem the DAVtq or the Exception.

Option Explicit

Dim ReadItemArguments1: Set ReadItemArguments1 = CreateObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")
ReadItemArguments1.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
ReadItemArguments1.ItemDescriptor.ItemID = "Simulation.Random"

Dim ReadItemArguments2: Set ReadItemArguments2 = CreateObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")
ReadItemArguments2.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
ReadItemArguments2.ItemDescriptor.ItemID = "UnknownItem"

Dim arguments(1)
Set arguments(0) = ReadItemArguments1
Set arguments(1) = ReadItemArguments2

Dim Client: Set Client = CreateObject("OpcLabs.EasyOpc.DataAccess.EasyDAClient")
Dim results: results = Client.ReadMultipleItems(arguments)

Dim i: For i = LBound(results) To UBound(results)
    Dim VtqResult: Set VtqResult = results(i)
    If VtqResult.Succeeded Then
        WScript.Echo "results(" & i & ").Vtq.ToString(): " & VtqResult.Vtq.ToString()
    Else
        WScript.Echo "results(" & i & ") *** Failure: " & VtqResult.ErrorMessageBrief
    End If
Next

Example 5

Rem This example attempts to read 3 items (first valid, second invalid, third valid again), and display their values, 
Rem timestamps and qualities. Without testing for a success, a run-time error occurs when accessing the Vtq property
Rem of a failed result.

Option Explicit

Dim ReadItemArguments1: Set ReadItemArguments1 = CreateObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")
ReadItemArguments1.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
ReadItemArguments1.ItemDescriptor.ItemID = "Simulation.Random"

Dim ReadItemArguments2: Set ReadItemArguments2 = CreateObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")
ReadItemArguments2.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
ReadItemArguments2.ItemDescriptor.ItemID = "UnknownItem"

Dim ReadItemArguments3: Set ReadItemArguments3 = CreateObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")
ReadItemArguments3.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
ReadItemArguments3.ItemDescriptor.ItemID = "Trends.Ramp (1 min)"

Dim arguments(2)
Set arguments(0) = ReadItemArguments1
Set arguments(1) = ReadItemArguments2
Set arguments(2) = ReadItemArguments3

Dim Client: Set Client = CreateObject("OpcLabs.EasyOpc.DataAccess.EasyDAClient")
Dim results: results = Client.ReadMultipleItems(arguments)

Dim i: For i = LBound(results) To UBound(results)
    ' This is an anti-example - you should not access the Vtq property without testing the success first!
    WScript.Echo "results(" & i & ").Vtq.ToString(): " & results(i).Vtq.ToString()
Next

Read parameters

In QuickOPC.NET, you can use the optional argument of type DAReadParameters, and then set the ValueAge property in it to control how “old” may be the values you receive by reading from OPC items.  With the DataSource property, you can also specify that you want values from the device, or from cache. You can also use the pre-defined DAReadParameters.CacheSource and DAReadParameters.DeviceSource constants to specify the read parameters. There are also overloads of ReadXXXX methods that accept an integer valueAge argument.

Some OPC-DA (Data Access) servers only support older versions of the OPC specifications, which do not allow specifying the value age by a number; they only support reading from the cache, and reading from the device. With such servers, QuickOPC may emulate this functionality by providing a value from its internal (client-side) cache, when it is fresh enough, and performing a read from the device otherwise.

In .NET languages, there is an implicit conversion operator from Int32 to DAReadParameters, which means that you can simply use the number of milliseconds that represents the value age in place of any argument that expects the read parameters (the DAReadParameters object). There is also a FromInt32 Method which has the same functionality as this conversion operator.

In addition, there is also an implicit conversion from the DADataSource Enumeration to DAReadParameters. You can therefore use the enumeration members such as DADataSource.Cache or DADataSource.Device in place of the read parameters. The FromDADataSource Method has the same functionality as this conversion operator. 

The default setting of read parameters, which specifies a non-zero value age, may sometimes "bite" you, if you expect to receive an up-to-date value from the data source. Furthermore, you may even receive a "bad quality" indication with some first reads, because the (OPC server) cache is not yet filled with valid data. Make sure to specify the value age that is appropriate for particular read operation in your application, if the default behavior is not what you want.

Reading from the device (or using very short value age) is, however, an ineffective practice that is discouraged, and should only be used when absolutely necessary.

Be aware that it is physically impossible for any system to always obtain fully up-to-date values all the time. 

 Include: Examples - OPC Data Access - Read a single item from the device 
// This example shows how to read a single item from the device, and display its value, timestamp and quality.

using System;
using OpcLabs.EasyOpc.DataAccess;
using OpcLabs.EasyOpc.OperationModel;

namespace DocExamples.DataAccess._EasyDAClient
{
    partial class ReadItem
    {
        public static void DeviceSource()
        {
            // Instantiate the client object.
            var client = new EasyDAClient();

            Console.WriteLine("Reading item...");
            DAVtq vtq;
            try
            {
                // DADataSource enumeration:
                // Selects the data source for OPC reads (from device, from OPC cache, or dynamically determined).
                // The data source (memory, OPC cache or OPC device) selection is based on the desired value age and
                // current status of data received from the server.

                vtq = client.ReadItem("OPCLabs.KitServer.2", "Simulation.Random", DADataSource.Device);
            }
            catch (OpcException opcException)
            {
                Console.WriteLine("*** Failure: {0}", opcException.GetBaseException().Message);
                return;
            }

            Console.WriteLine("Vtq: {0}", vtq);
        }
    }
}

// This example shows how to read 4 items from the device, and display their values, timestamps and qualities.

using System;
using System.Diagnostics;
using OpcLabs.EasyOpc.DataAccess;
using OpcLabs.EasyOpc.DataAccess.OperationModel;

namespace DocExamples.DataAccess._EasyDAClient
{
    partial class ReadMultipleItems
    {
        public static void DeviceSource()
        {
            // Instantiate the client object.
            var client = new EasyDAClient();

            // DADataSource enumeration:
            // Selects the data source for OPC reads (from device, from OPC cache, or dynamically determined).
            // The data source (memory, OPC cache or OPC device) selection will be based on the desired value age and
            // current status of data received from the server.

            DAVtqResult[] vtqResults = client.ReadMultipleItems(
                new []
                    {
                        new DAReadItemArguments("OPCLabs.KitServer.2", "Simulation.Random", DADataSource.Device),
                        new DAReadItemArguments("OPCLabs.KitServer.2", "Trends.Ramp (1 min)", DADataSource.Device),
                        new DAReadItemArguments("OPCLabs.KitServer.2", "Trends.Sine (1 min)", DADataSource.Device),
                        new DAReadItemArguments("OPCLabs.KitServer.2", "Simulation.Register_I4", DADataSource.Device)
                    });

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

                if (vtqResults[i].Succeeded)
                    Console.WriteLine("vtqResult[{0}].Vtq: {1}", i, vtqResults[i].Vtq);
                else
                    Console.WriteLine("vtqResult[{0}] *** Failure: {1}", i, vtqResults[i].ErrorMessageBrief);
            }
        }


        // Example output:
        //
        //vtqResult[0].Vtq: 0.00125125888851588 { System.Double} @2020-04-10T12:44:16.250; GoodNonspecific(192)
        //vtqResult[1].Vtq: 0.270812898874283 {System.Double} @2020-04-10T12:44:16.248; GoodNonspecific(192)
        //vtqResult[2].Vtq: 0.991434340167834 {System.Double} @2020-04-10T12:44:16.250; GoodNonspecific(192)
        //vtqResult[3].Vtq: 0 {System.Int32} @1601-01-01T00:00:00.000; GoodNonspecific(192)
    }
}

Rem This example shows how to read 4 items from the device, and display their values, timestamps and qualities.

Option Explicit

' Selects the data source for OPC reads (from device, from OPC cache, or dynamically determined).
' The data source (memory, OPC cache or OPC device) selection will be based on the desired value age and current status of 
' data received from the server.
Const DADataSource_ByValueAge = 0
' OPC reads will be fulfilled from the cache in the OPC server.
Const DADataSource_Cache = 1
' OPC reads will be fulfilled from the device by the OPC server.
Const DADataSource_Device = 2

Dim ReadItemArguments1: Set ReadItemArguments1 = CreateObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")
ReadItemArguments1.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
ReadItemArguments1.ItemDescriptor.ItemID = "Simulation.Random"
ReadItemArguments1.ReadParameters.DataSource = DADataSource_Device  ' read will be from device

Dim ReadItemArguments2: Set ReadItemArguments2 = CreateObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")
ReadItemArguments2.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
ReadItemArguments2.ItemDescriptor.ItemID = "Trends.Ramp (1 min)"
ReadItemArguments2.ReadParameters.DataSource = DADataSource_Device  ' read will be from device

Dim ReadItemArguments3: Set ReadItemArguments3 = CreateObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")
ReadItemArguments3.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
ReadItemArguments3.ItemDescriptor.ItemID = "Trends.Sine (1 min)"
ReadItemArguments3.ReadParameters.DataSource = DADataSource_Device  ' read will be from device

Dim ReadItemArguments4: Set ReadItemArguments4 = CreateObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")
ReadItemArguments4.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
ReadItemArguments4.ItemDescriptor.ItemID = "Simulation.Register_I4"
ReadItemArguments4.ReadParameters.DataSource = DADataSource_Device  ' read will be from device

Dim arguments(3)
Set arguments(0) = ReadItemArguments1
Set arguments(1) = ReadItemArguments2
Set arguments(2) = ReadItemArguments3
Set arguments(3) = ReadItemArguments4

Dim Client: Set Client = CreateObject("OpcLabs.EasyOpc.DataAccess.EasyDAClient")

Dim results: results = Client.ReadMultipleItems(arguments)

Dim i: For i = LBound(results) To UBound(results)
    Dim VtqResult: Set VtqResult = results(i)
    If VtqResult.Succeeded Then
        WScript.Echo "results(" & i & ").Vtq.ToString(): " & VtqResult.Vtq.ToString()
    Else
        WScript.Echo "results(" & i & ") *** Failure: " & VtqResult.ErrorMessageBrief
    End If
Next

 

Inheritance Hierarchy

System.Object
   OpcLabs.BaseLib.Object2
      OpcLabs.BaseLib.Info
         OpcLabs.BaseLib.OperationModel.OperationResult
            OpcLabs.EasyOpc.DataAccess.OperationModel.DAVtqResult
               OpcLabs.EasyOpc.DataAccess.Generic.DAVtqResult<TValue>

Requirements

Target Platforms: .NET Framework: Windows 10 (selected versions), Windows 11 (selected versions), Windows Server 2012, Windows Server 2016; .NET Core, .NET 5, .NET 6: Linux, macOS, Microsoft Windows

See Also

Reference

DAVtqResult Members
OpcLabs.EasyOpc.DataAccess.OperationModel Namespace

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