Examples - OPC Data Access - Get values of multiple properties

Basic example

.NET

// This example shows how to get value of multiple OPC properties, and handle errors.
//
// Note that some properties may not have a useful value initially (e.g. until the item is activated in a group), which also the
// case with Timestamp property as implemented by the demo server. This behavior is server-dependent, and normal. You can run 
// IEasyDAClient.ReadMultipleItemValues.Main.vbs shortly before this example, in order to obtain better property values. Your 
// code may also subscribe to the items in order to assure that they remain active.

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

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

            ServerDescriptor serverDescriptor = "OPCLabs.KitServer.2";

            // Get the values of Timestamp and AccessRights properties of two items.
            ValueResult[] results = client.GetMultiplePropertyValues(new[]
            {
                new DAPropertyArguments(serverDescriptor, "Simulation.Random", DAPropertyDescriptor.Timestamp),
                new DAPropertyArguments(serverDescriptor, "Simulation.Random", DAPropertyDescriptor.AccessRights),
                new DAPropertyArguments(serverDescriptor, "Trends.Ramp (1 min)", DAPropertyDescriptor.Timestamp),
                new DAPropertyArguments(serverDescriptor, "Trends.Ramp (1 min)", DAPropertyDescriptor.AccessRights)
            });

            for (int i = 0; i < results.Length; i++)
            {
                ValueResult valueResult = results[i];
                if (valueResult.Exception is null)
                    Console.WriteLine($"results({i}).Value: {valueResult.Value}");
                else
                    Console.WriteLine($"results({i}).Exception.Message: {valueResult.Exception.Message}");
            }
        }
    }
}

# This example shows how to get value of multiple OPC properties, and handle errors.
#
# Note that some properties may not have a useful value initially (e.g. until the item is activated in a group), which also the
# case with Timestamp property as implemented by the demo server. This behavior is server-dependent, and normal. You can run
# IEasyDAClient.ReadItemValue.Main.vbs shortly before this example, in order to obtain better property values. Your code may
# also subscribe to the item in order to assure that it remains active.

# The QuickOPC package is needed. Install it using "pip install opclabs_quickopc".
import opclabs_quickopc

# Import .NET namespaces.
from OpcLabs.EasyOpc import *
from OpcLabs.EasyOpc.DataAccess import *
from OpcLabs.EasyOpc.DataAccess.OperationModel import *
from OpcLabs.EasyOpc.OperationModel import *


serverDescriptor = ServerDescriptor('OPCLabs.KitServer.2')

# Instantiate the client object.
client = EasyDAClient()

# Get the values of Timestamp and AccessRights properties of two items.
resultArray = client.GetMultiplePropertyValues([
    DAPropertyArguments(serverDescriptor, DAItemDescriptor('Simulation.Random'), DAPropertyDescriptor.Timestamp),
    DAPropertyArguments(serverDescriptor, DAItemDescriptor('Simulation.Random'), DAPropertyDescriptor.AccessRights),
    DAPropertyArguments(serverDescriptor, DAItemDescriptor('Trends.Ramp (1 min)'), DAPropertyDescriptor.Timestamp),
    DAPropertyArguments(serverDescriptor, DAItemDescriptor('Trends.Ramp (1 min)'), DAPropertyDescriptor.AccessRights),
    ])

# Display results
for i, valueResult in enumerate(resultArray):
    valueResult = resultArray[i]
    if valueResult.Exception is None:
        print('resultArray[', i, '].Value: ', valueResult.Value, sep='')
    else:
        print('resultArray[', i, '].Exception.Message: ', valueResult.Exception.Message, sep='')

# This example shows how to get value of multiple OPC properties, and handle errors.
#
# Note that some properties may not have a useful value initially (e.g. until the item is activated in a group), which also the
# case with Timestamp property as implemented by the demo server. This behavior is server-dependent, and normal. You can run 
# IEasyDAClient.ReadMultipleItemValues.Main.vbs shortly before this example, in order to obtain better property values. Your 
# code may also subscribe to the items in order to assure that they remain active.

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

# The path below assumes that the current directory is [ProductDir]/Examples-NET/PowerShell/Windows .
Add-Type -Path "../../../Components/Opclabs.QuickOpc/net472/OpcLabs.EasyOpcClassicCore.dll"
Add-Type -Path "../../../Components/Opclabs.QuickOpc/net472/OpcLabs.EasyOpcClassic.dll"
Add-Type -Path "../../../Components/Opclabs.QuickOpc/net472/OpcLabs.EasyOpcClassicComponents.dll"

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

$serverDescriptor = New-Object ServerDescriptor("OPCLabs.KitServer.2")

# Get the values of Timestamp and AccessRights properties of two items.
$results = $client.GetMultiplePropertyValues(@(
    (New-Object DAPropertyArguments($serverDescriptor, "Simulation.Random", [DAPropertyDescriptor]::Timestamp)),
    (New-Object DAPropertyArguments($serverDescriptor, "Simulation.Random", [DAPropertyDescriptor]::AccessRights)),
    (New-Object DAPropertyArguments($serverDescriptor, "Trends.Ramp (1 min)", [DAPropertyDescriptor]::Timestamp)),
    (New-Object DAPropertyArguments($serverDescriptor, "Trends.Ramp (1 min)", [DAPropertyDescriptor]::AccessRights))
    ))

for ($i = 0; $i -lt $results.Length; $i++) {
    $valueResult = $results[$i]
    if ($valueResult.Exception -eq $null) {
        Write-Host "results($($i)).Value: $($valueResult.Value)"
    }
    else {
        Write-Host "results($($i)).Exception.Message: $($valueResult.Exception.Message)"
    }
}

COM

// This example shows how to get value of multiple OPC properties.
//
// Note that some properties may not have a useful value initially (e.g. until the item is activated in a group), which also the
// case with Timestamp property as implemented by the demo server. This behavior is server-dependent, and normal. You can run
// IEasyDAClient.ReadMultipleItemValues.Main.vbs shortly before this example, in order to obtain better property values. Your
// code may also subscribe to the items in order to assure that they remain active.

class procedure GetMultiplePropertyValues.Main;
var
  Arguments: OleVariant;
  Client: OpcLabs_EasyOpcClassic_TLB._EasyDAClient;
  I: Cardinal;
  PropertyArguments1: _DAPropertyArguments;
  PropertyArguments2: _DAPropertyArguments;
  PropertyArguments3: _DAPropertyArguments;
  PropertyArguments4: _DAPropertyArguments;
  ValueResult: _ValueResult;
  Results: OleVariant;
begin

  // Get the values of Timestamp and AccessRights properties of two items.

  PropertyArguments1 := CoDAPropertyArguments.Create;
  PropertyArguments1.ServerDescriptor.ServerClass := 'OPCLabs.KitServer.2';
  PropertyArguments1.NodeDescriptor.ItemID := 'Simulation.Random';
  PropertyArguments1.PropertyDescriptor.PropertyId.NumericalValue := DAPropertyIds_Timestamp;

  PropertyArguments2 := CoDAPropertyArguments.Create;
  PropertyArguments2.ServerDescriptor.ServerClass := 'OPCLabs.KitServer.2';
  PropertyArguments2.NodeDescriptor.ItemID := 'Simulation.Random';
  PropertyArguments2.PropertyDescriptor.PropertyId.NumericalValue := DAPropertyIds_AccessRights;

  PropertyArguments3 := CoDAPropertyArguments.Create;
  PropertyArguments3.ServerDescriptor.ServerClass := 'OPCLabs.KitServer.2';
  PropertyArguments3.NodeDescriptor.ItemID := 'Trends.Ramp (1 min)';
  PropertyArguments3.PropertyDescriptor.PropertyId.NumericalValue := DAPropertyIds_Timestamp;

  PropertyArguments4 := CoDAPropertyArguments.Create;
  PropertyArguments4.ServerDescriptor.ServerClass := 'OPCLabs.KitServer.2';
  PropertyArguments4.NodeDescriptor.ItemID := 'Trends.Ramp (1 min)';
  PropertyArguments4.PropertyDescriptor.PropertyId.NumericalValue := DAPropertyIds_AccessRights;

  Arguments := VarArrayCreate([0, 3], varVariant);
  Arguments[0] := PropertyArguments1;
  Arguments[1] := PropertyArguments2;
  Arguments[2] := PropertyArguments3;
  Arguments[3] := PropertyArguments4;

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

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

  // Display results
  for I := VarArrayLowBound(Results, 1) to VarArrayHighBound(Results, 1) do
  begin
      ValueResult := IInterface(Results[I]) as _ValueResult;

      // Check if there has been an error getting the property value
      if ValueResult.Exception <> nil then
      begin
        WriteLn(Format('s *** Failures', [Arguments[I].NodeDescriptor.NodeId, ValueResult.Exception.Message]));
        Continue;
      end;

      WriteLn('results(', i, ').Value: ', ValueResult.Value);
  end;
  VarClear(Results);
  VarClear(Arguments);
end;

// This example shows how to get value of multiple OPC properties, and handle errors.
//
// Note that some properties may not have a useful value initially (e.g. until the item is activated in a group), which also the
// case with Timestamp property as implemented by the demo server. This behavior is server-dependent, and normal. You can run 
// IEasyDAClient.ReadMultipleItemValues.Main.vbs shortly before this example, in order to obtain better property values. Your 
// code may also subscribe to the items in order to assure that they remain active.

const Timestamp = 4;
const AccessRights = 5;

// Get the values of Timestamp and AccessRights properties of two items.

$PropertyArguments1 = new COM("OpcLabs.EasyOpc.DataAccess.OperationModel.DAPropertyArguments");
$PropertyArguments1->ServerDescriptor->ServerClass = "OPCLabs.KitServer.2";
$PropertyArguments1->NodeDescriptor->ItemID = "Simulation.Random";
$PropertyArguments1->PropertyDescriptor->PropertyID->NumericalValue = Timestamp;

$PropertyArguments2 = new COM("OpcLabs.EasyOpc.DataAccess.OperationModel.DAPropertyArguments");
$PropertyArguments2->ServerDescriptor->ServerClass = "OPCLabs.KitServer.2";
$PropertyArguments2->NodeDescriptor->ItemID = "Simulation.Random";
$PropertyArguments2->PropertyDescriptor->PropertyID->NumericalValue = AccessRights;

$PropertyArguments3 = new COM("OpcLabs.EasyOpc.DataAccess.OperationModel.DAPropertyArguments");
$PropertyArguments3->ServerDescriptor->ServerClass = "OPCLabs.KitServer.2";
$PropertyArguments3->NodeDescriptor->ItemID = "Trends.Ramp (1 min)";
$PropertyArguments3->PropertyDescriptor->PropertyID->NumericalValue = Timestamp;

$PropertyArguments4 = new COM("OpcLabs.EasyOpc.DataAccess.OperationModel.DAPropertyArguments");
$PropertyArguments4->ServerDescriptor->ServerClass = "OPCLabs.KitServer.2";
$PropertyArguments4->NodeDescriptor->ItemID = "Trends.Ramp (1 min)";
$PropertyArguments4->PropertyDescriptor->PropertyID->NumericalValue = AccessRights;

$arguments[0] = $PropertyArguments1;
$arguments[1] = $PropertyArguments2;
$arguments[2] = $PropertyArguments3;
$arguments[3] = $PropertyArguments4;

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

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

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

Rem This example shows how to get value of multiple OPC properties.
Rem
Rem Note that some properties may not have a useful value initially (e.g. until the item is activated in a group), which also the
Rem case with Timestamp property as implemented by the demo server. This behavior is server-dependent, and normal. You can run
Rem IEasyDAClient.ReadMultipleItemValues.Main.vbs shortly before this example, in order to obtain better property values. Your
Rem code may also subscribe to the items in order to assure that they remain active.

Private Sub GetMultiplePropertyValues_Main_Command_Click()
    OutputText = ""
    
    ' Get the values of Timestamp and AccessRights properties of two items.

    Dim propertyArguments1 As New DAPropertyArguments
    propertyArguments1.serverDescriptor.ServerClass = "OPCLabs.KitServer.2"
    propertyArguments1.nodeDescriptor.itemId = "Simulation.Random"
    propertyArguments1.PropertyDescriptor.propertyId.NumericalValue = DAPropertyIds_Timestamp
    
    Dim propertyArguments2 As New DAPropertyArguments
    propertyArguments2.serverDescriptor.ServerClass = "OPCLabs.KitServer.2"
    propertyArguments2.nodeDescriptor.itemId = "Simulation.Random"
    propertyArguments2.PropertyDescriptor.propertyId.NumericalValue = DAPropertyIds_AccessRights
    
    Dim propertyArguments3 As New DAPropertyArguments
    propertyArguments3.serverDescriptor.ServerClass = "OPCLabs.KitServer.2"
    propertyArguments3.nodeDescriptor.itemId = "Trends.Ramp (1 min)"
    propertyArguments3.PropertyDescriptor.propertyId.NumericalValue = DAPropertyIds_Timestamp
    
    Dim propertyArguments4 As New DAPropertyArguments
    propertyArguments4.serverDescriptor.ServerClass = "OPCLabs.KitServer.2"
    propertyArguments4.nodeDescriptor.itemId = "Trends.Ramp (1 min)"
    propertyArguments4.PropertyDescriptor.propertyId.NumericalValue = DAPropertyIds_AccessRights
    
    Dim arguments(3) As Variant
    Set arguments(0) = propertyArguments1
    Set arguments(1) = propertyArguments2
    Set arguments(2) = propertyArguments3
    Set arguments(3) = propertyArguments4

    ' Instantiate the client object
    Dim client As New EasyDAClient

    ' Obtain values. By default, the Value attributes of the nodes will be read.
    Dim results() As Variant
    results = client.GetMultiplePropertyValues(arguments)

    ' Display results
    Dim i: For i = LBound(results) To UBound(results)
        Dim valueResult As valueResult: Set valueResult = results(i)
        ' Check if there has been an error getting the property value
        If Not valueResult.Exception Is Nothing Then
            OutputText = OutputText & arguments(i).nodeDescriptor.NodeId & " *** Failure: " & valueResult.Exception.Message & vbCrLf
        Else
            OutputText = OutputText & "results(" & i & ").Value: " & valueResult.value & vbCrLf
        End If
    Next
End Sub

Rem This example shows how to get value of multiple OPC properties, and handle errors.
Rem
Rem Note that some properties may not have a useful value initially (e.g. until the item is activated in a group), which also the
Rem case with Timestamp property as implemented by the demo server. This behavior is server-dependent, and normal. You can run 
Rem IEasyDAClient.ReadMultipleItemValues.Main.vbs shortly before this example, in order to obtain better property values. Your 
Rem code may also subscribe to the items in order to assure that they remain active.

Option Explicit

Const Timestamp = 4
Const AccessRights = 5

' Get the values of Timestamp and AccessRights properties of two items.

Dim PropertyArguments1: Set PropertyArguments1 = CreateObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAPropertyArguments")
PropertyArguments1.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
PropertyArguments1.NodeDescriptor.ItemID = "Simulation.Random"
PropertyArguments1.PropertyDescriptor.PropertyID.NumericalValue = Timestamp

Dim PropertyArguments2: Set PropertyArguments2 = CreateObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAPropertyArguments")
PropertyArguments2.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
PropertyArguments2.NodeDescriptor.ItemID = "Simulation.Random"
PropertyArguments2.PropertyDescriptor.PropertyID.NumericalValue = AccessRights

Dim PropertyArguments3: Set PropertyArguments3 = CreateObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAPropertyArguments")
PropertyArguments3.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
PropertyArguments3.NodeDescriptor.ItemID = "Trends.Ramp (1 min)"
PropertyArguments3.PropertyDescriptor.PropertyID.NumericalValue = Timestamp

Dim PropertyArguments4: Set PropertyArguments4 = CreateObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAPropertyArguments")
PropertyArguments4.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
PropertyArguments4.NodeDescriptor.ItemID = "Trends.Ramp (1 min)"
PropertyArguments4.PropertyDescriptor.PropertyID.NumericalValue = AccessRights

Dim arguments(3)
Set arguments(0) = PropertyArguments1
Set arguments(1) = PropertyArguments2
Set arguments(2) = PropertyArguments3
Set arguments(3) = PropertyArguments4

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

Dim i: For i = LBound(results) To UBound(results)
    If results(i).Exception Is Nothing Then 
        WScript.Echo "results(" & i & ").Value: " & results(i).Value
    Else
        WScript.Echo "results(" & i & ").Exception.Message: " & results(i).Exception.Message
    End If
Next

Example with time measurement

VBScript

Rem This example measures the time needed to get values of all OPC properties of a single OPC item all at once.
Rem This example shows how to get value of multiple OPC properties.

Option Explicit

Dim ServerDescriptor: Set ServerDescriptor = CreateObject("OpcLabs.EasyOpc.ServerDescriptor")
ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"

Dim NodeDescriptor: Set NodeDescriptor = CreateObject("OpcLabs.EasyOpc.DataAccess.DANodeDescriptor")
NodeDescriptor.ItemID = "Simulation.ReadValue_I4"

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

Dim PropertyElementCollection
On Error Resume Next
Set PropertyElementCollection = Client.BrowseProperties(ServerDescriptor, NodeDescriptor)
If Err.Number <> 0 Then
    WScript.Echo "*** Failure: " & Err.Source & ": " & Err.Description
    WScript.Quit
End If
On Error Goto 0

Dim count: count = PropertyElementCollection.Count

Dim arguments(): Redim arguments(count - 1)
Dim i: i = 0
Dim PropertyElement: For Each PropertyElement In PropertyElementCollection
    Dim PropertyArguments: Set PropertyArguments = CreateObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAPropertyArguments")
    PropertyArguments.ServerDescriptor = ServerDescriptor
    PropertyArguments.NodeDescriptor = NodeDescriptor
    PropertyArguments.PropertyDescriptor.PropertyID = PropertyElement.PropertyId

    Set arguments(i) = PropertyArguments
    i = i + 1
Next

'EasyDAClient.ReadItemValue "", "OPCLabs.KitServer.2", "Simulation.ReadValue_I4"
Dim startTime: startTime = Timer
Dim results: results = Client.GetMultiplePropertyValues(arguments)
WScript.Echo "Time taken (milliseconds): " & (Timer - startTime)*1000

'For i = LBound(results) To UBound(results)
'    If results(i).Exception Is Nothing Then 
'        WScript.Echo "results(" & i & ").Value: " & results(i).Value
'    Else
'        WScript.Echo "results(" & i & ").Exception.Message: " & results(i).Exception.Message
'    End If
''Next

Example combined with item browsing

The example below is a bit more complex, and combines the ability to browse for items with getting the data type property for each of the items obtained.

// This example shows how to obtain a data type of all OPC items under a branch.

using System;
using System.Linq;
using OpcLabs.BaseLib.ComInterop;
using OpcLabs.BaseLib.OperationModel;
using OpcLabs.EasyOpc;
using OpcLabs.EasyOpc.DataAccess;
using OpcLabs.EasyOpc.DataAccess.AddressSpace;

namespace DocExamples.DataAccess._EasyDAClient
{
    partial class GetMultiplePropertyValues
    {
        public static void DataType()
        {
            // Instantiate the client object.
            var client = new EasyDAClient();
            ServerDescriptor serverDescriptor = "OPCLabs.KitServer.2";

            // Browse for all leaves under the "Simulation" branch
            DANodeElementCollection nodeElementCollection = client.BrowseLeaves(serverDescriptor, "Simulation");

            // Create list of node descriptors, one for each leaf obtained
            DANodeDescriptor[] nodeDescriptorArray = nodeElementCollection
                .Where(element => !element.IsHint)  // filter out hint leafs that do not represent real OPC items (rare)
                .Select(element => new DANodeDescriptor(element))
                .ToArray();

            // Get the value of DataType property; it is a 16-bit signed integer
            ValueResult[] valueResultArray = client.GetMultiplePropertyValues(serverDescriptor,
                nodeDescriptorArray, DAPropertyIds.DataType);

            for (int i = 0; i < valueResultArray.Length; i++)
            {
                DANodeDescriptor nodeDescriptor = nodeDescriptorArray[i];

                // Check if there has been an error getting the property value
                ValueResult valueResult = valueResultArray[i];
                if (!(valueResult.Exception is null))
                {
                    Console.WriteLine("{0} *** Failure: {1}", nodeDescriptor.NodeId, valueResult.Exception.Message);
                    continue;
                }

                // Convert the data type to VarType
                var varType = (VarType)(short)valueResult.Value;

                // Display the obtained data type
                Console.WriteLine("{0}: {1}", nodeDescriptor.ItemId, varType);
            }
        }
    }
}

# This example shows how to obtain a data type of all OPC items under a branch.

# The QuickOPC package is needed. Install it using "pip install opclabs_quickopc".
import opclabs_quickopc

# Import .NET namespaces.
from OpcLabs.BaseLib.ComInterop import *
from OpcLabs.EasyOpc import *
from OpcLabs.EasyOpc.DataAccess import *
from OpcLabs.EasyOpc.DataAccess.OperationModel import *
from OpcLabs.EasyOpc.OperationModel import *


serverDescriptor = ServerDescriptor('OPCLabs.KitServer.2')

# Instantiate the client object.
client = EasyDAClient()

# Browse for all leaves under the "Simulation" branch.
try:
    nodeElementCollection = IEasyDAClientExtension.BrowseLeaves(client, serverDescriptor, DANodeDescriptor('Simulation'))
except OpcException as opcException:
    print('*** Failure: ' + opcException.GetBaseException().Message)
    exit()

# Create list of node descriptors, one for each leaf obtained.
filteredNodeElements = filter(lambda element: not element.IsHint, nodeElementCollection)
nodeDescriptorArray = list(map(lambda element: DANodeDescriptor(element), filteredNodeElements))

# Get the value of DataType property; it is a 16-bit signed integer.
resultArray = IEasyDAClientExtension.GetMultiplePropertyValues(client,
                                                               serverDescriptor,
                                                               nodeDescriptorArray,
                                                               DAPropertyDescriptor.FromInt64(DAPropertyIds.DataType))
# Display results
for i, valueResult in enumerate(resultArray):
    nodeDescriptor = nodeDescriptorArray[i]
    # Check if there has been an error getting the property value.
    if valueResult.Exception is  None:
        # Convert the data type to VarType.
        varType = VarType(valueResult.Value)
        # Display the obtained data type.
        print(nodeDescriptor.ItemId, ': ', varType, sep='')
    else:
        print(nodeDescriptor.ItemId, ' *** Failure: ', valueResult.Exception.Message)

' This example shows how to obtain a data type of all OPC items under a branch.

Imports OpcLabs.BaseLib.ComInterop
Imports OpcLabs.BaseLib.OperationModel
Imports OpcLabs.EasyOpc
Imports OpcLabs.EasyOpc.DataAccess

Namespace DataAccess._EasyDAClient
    Friend Class GetMultiplePropertyValues
        Public Shared Sub DataType()
            Dim client = New EasyDAClient()
            Dim serverDescriptor As ServerDescriptor = "OPCLabs.KitServer.2"

            ' Browse for all leaves under the "Simulation" branch
            Dim nodeElementCollection = client.BrowseLeaves(serverDescriptor, "Simulation")

            ' Create list of node descriptors, one for each leaf obtained
            ' filter out hint leafs that do not represent real OPC items (rare)
            Dim nodeDescriptorArray() As DANodeDescriptor = nodeElementCollection _
                .Where(Function(element) Not element.IsHint) _
                .Select(Function(element) New DANodeDescriptor(element)) _
                .ToArray()

            ' Get the value of DataType property; it is a 16-bit signed integer
            Dim valueResultArray() As ValueResult = client.GetMultiplePropertyValues(serverDescriptor,
                    nodeDescriptorArray, DAPropertyIds.DataType)

            For i = 0 To valueResultArray.Length - 1
                Dim nodeDescriptor = nodeDescriptorArray(i)

                ' Check if there has been an error getting the property value
                Dim valueResult As ValueResult = valueResultArray(i)
                If valueResult.Exception IsNot Nothing Then
                    Console.WriteLine("{0} *** Failure: {1}", nodeDescriptor.NodeId, valueResult.Exception.Message)
                    Continue For
                End If

                ' Convert the data type to VarType
                Dim varType = CType(CShort(valueResult.Value), VarType)

                ' Display the obtained data type
                Console.WriteLine("{0}: {1}", nodeDescriptor.ItemId, varType)
            Next i
        End Sub
    End Class
End Namespace

Basic example

.NET

COM

Example with time measurement

Example combined with item browsing

Examples - OPC DA Layered Extensions

Conceptual

Examples - OPC XML-DA