OPC Studio User's Guide and Reference
Getting OPC Classic Property Values
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Concepts > QuickOPC Concepts > QuickOPC Development Models > Imperative Programming Model > Imperative Programming Model for OPC Data (Classic and UA) > Obtaining Information (OPC Data) > Getting OPC Classic Property Values
In This Topic

Each OPC item has typically associated a set of OPC properties with it. OPC properties contain additional information related to the item.

Except in special cases with clear justification, do not use the OPC Classic property mechanism to get "dynamic" properties such as Value, Quality, or Timestamp. Doing so is very inefficient and has additional issues associated with it (reliability, consistency). Use normal read or subscriptions instead.

A single property

If you want to obtain the value of specific OPC property, call the GetPropertyValue method, passing it the machine name, server class, the ItemId, and a PropertyId. You will receive back an Object (a VARIANT in QuickOPC-COM) containing the value of the requested property.

In QuickOPC.NET, you can also pass in the ServerDescriptor in place of the machine name and server class strings.

In addition to basic methods, there are also many property-related methods. Please refer to a chapter in this document that describes EasyOPC.NET Extensions.

OPC Data Access

Basic example

.NET

// This example shows how to get a value of a single OPC property.
//
// 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.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// OPC client and subscriber examples in C# on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-CSharp .
// Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
// a commercial license in order to use Online Forums, and we reply to every post.

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

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

            object value;
            try
            {
                value = client.GetPropertyValue("", "OPCLabs.KitServer.2", "Simulation.Random",
                    DAPropertyIds.Timestamp);
            }
            catch (OpcException opcException)
            {
                Console.WriteLine("*** Failure: {0}", opcException.GetBaseException().Message);
                return;
            }

            Console.WriteLine(value);
        }
    }
}

COM

// This example shows how to get a value of a single OPC property.
//
// 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.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// OPC client and subscriber examples in PHP on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-PHP .
// Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
// a commercial license in order to use Online Forums, and we reply to every post.

const Timestamp = 4;

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

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

printf("%s\n", $value);

Python

# This example shows how to get a value of a single OPC property.
#
# 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.
#
# Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
# OPC client and subscriber examples in Python on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-Python .
# Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
# a commercial license in order to use Online Forums, and we reply to every post.
# The QuickOPC package is needed. Install it using "pip install opclabs_quickopc".
import opclabs_quickopc

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


# Instantiate the client object
client = EasyDAClient()

# Perform the operation
try:
    value = IEasyDAClientExtension.GetPropertyValue(client,
        '', 'OPCLabs.KitServer.2', 'Simulation.Random', DAPropertyId(DAPropertyIds.Timestamp))
except OpcException as opcException:
    print('*** Failure: ' + opcException.GetBaseException().Message)
    exit()

# Display results
print('value: ', value, sep='')

Example with time measurement

Rem This example measures the time needed to get values of all OPC properties of a single OPC item "one by one".
Rem
Rem Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
Rem OPC client and subscriber examples in VBScript on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VBScript .
Rem Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
Rem a commercial license in order to use Online Forums, and we reply to every post.

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

'EasyDAClient.ReadItemValue "", "OPCLabs.KitServer.2", "Simulation.ReadValue_I4"
Dim startTime: startTime = Timer
Dim PropertyElement: For Each PropertyElement In PropertyElementCollection
    Dim propertyID: Set propertyID = PropertyElement.PropertyID
    On Error Resume Next
    Dim value: value = Client.GetPropertyValue("", "OPCLabs.KitServer.2", "Simulation.ReadValue_I4", propertyID.NumericalValue)
    If Err.Number <> 0 Then
        WScript.Echo "*** Failure: " & Err.Source & ": " & Err.Description
        WScript.Quit
    End If
    On Error Goto 0
    'WScript.Echo value
Next
WScript.Echo "Time taken (milliseconds): " & (Timer - startTime)*1000

Example with type casting

The GetPropertyValue Method returns a generic object, regardless of the property involved. You may therefore need to cast the returned value to the expected type, and possibly do further processing on the value, as in the the example below.

.NET

// This example shows how to obtain a data type of an OPC item.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// OPC client and subscriber examples in C# on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-CSharp .
// Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
// a commercial license in order to use Online Forums, and we reply to every post.

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

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

            // Get the value of DataType property; it is a 16-bit signed integer
            short dataType;
            try
            {
                dataType = (short)client.GetPropertyValue("", "OPCLabs.KitServer.2", "Simulation.Random",
                    DAPropertyIds.DataType);
            }
            catch (OpcException opcException)
            {
                Console.WriteLine("*** Failure: {0}", opcException.GetBaseException().Message);
                return;
            }
            // Convert the data type to VarType
            var varType = (VarType)dataType;

            // Display the obtained data type
            Console.WriteLine("DataType: {0}", dataType);   // Display data type as numerical value
            Console.WriteLine("VarType: {0}", varType);     // Display data type symbolically

            // Code below illustrates how decisions can be made based on type
            switch (varType.InternalValue)
            {
                case VarTypes.R8:
                    Console.WriteLine("The data type is VarTypes.R8, as we expected.");
                    break;

                // other cases may come here ...

                default:
                    Console.WriteLine("The data type is not as we expected!");
                    break;
            }
        }
    }
}

Python

# This example shows how to obtain a data type of an OPC item.
#
# Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
# OPC client and subscriber examples in Python on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-Python .
# Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
# a commercial license in order to use Online Forums, and we reply to every post.
# 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.DataAccess import *
from OpcLabs.EasyOpc.OperationModel import *


# Instantiate the client object.
client = EasyDAClient()

# Get the value of DataType property; it is a 16-bit signed integer.
try:
    dataType = IEasyDAClientExtension.GetPropertyValue(client,
        '', 'OPCLabs.KitServer.2', 'Simulation.Random', DAPropertyId(DAPropertyIds.DataType))
except OpcException as opcException:
    print('*** Failure: ' + opcException.GetBaseException().Message)
    exit()
# Convert the data type to VarType.
varType = VarType(dataType)

# Display the obtained data type.
print('DataType: ', dataType, sep='')   # Display data type as numerical value
print('VarType: ', varType, sep='')     # Display data type symbolically

# Code below illustrates how decisions can be made based on type
if varType.InternalValue == VarTypes.R8:
    print('The data type is VarTypes.R8, as we expected.')
# other cases may come here ...
else:
    print('The data type is not as we expected!')

 

OPC XML-DA

.NET

// This example shows how to get a value of a single OPC XML-DA property.
//
// 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.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// OPC client and subscriber examples in C# on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-CSharp .
// Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
// a commercial license in order to use Online Forums, and we reply to every post.

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

namespace DocExamples.DataAccess.Xml
{
    partial class GetPropertyValue
    {
        public static void Main1Xml()
        {
            // Instantiate the client object.
            var client = new EasyDAClient();

            object value;
            try
            {
                value = client.GetPropertyValue("http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx", "Dynamic/Analog Types/Int",
                    DAPropertyDescriptor.Timestamp);
            }
            catch (OpcException opcException)
            {
                Console.WriteLine("*** Failure: {0}", opcException.GetBaseException().Message);
                return;
            }

            Console.WriteLine(value);
        }
    }
}

Python

# This example shows how to get a value of a single OPC XML-DA property.
#
# Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
# OPC client and subscriber examples in Python on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-Python .
# Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
# a commercial license in order to use Online Forums, and we reply to every post.
# 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 *

# Instantiate the client object.
client = EasyDAClient()

# Perform the operation
try:
    value = IEasyDAClientExtension.GetPropertyValue(client, ServerDescriptor('http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx'), DANodeDescriptor('Dynamic/Analog Types/Int'), 
                                                    DAPropertyDescriptor(DAPropertyId(DAPropertyDescriptor.Timestamp)))
except OpcException as opcException:
    print('*** Failure: ' + opcException.GetBaseException().Message, sep='')
    exit()

# Display results
print('value: ', value, sep='')

 

QuickOPC supports OPC XML-DA also on Linux and macOS.

 

Multiple properties

For obtaining multiple properties simultaneously in an efficient manner, call the GetMultiplePropertyValues method (instead of multiple GetPropertyValue calls in a loop). The arguments are similar, except that in place of a single PropertyId you pass in an array of them. You will receive back an array of Object values (a SAFEARRAY of VARIANT values in QuickOPC-COM).

OPC Data Access

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.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// OPC client and subscriber examples in C# on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-CSharp .
// Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
// a commercial license in order to use Online Forums, and we reply to every post.

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}");
            }
        }
    }
}

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.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// OPC client and subscriber examples in Object Pascal (Delphi) on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-OP .
// Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
// a commercial license in order to use Online Forums, and we reply to every post.

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;

Python

# 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.
#
# Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
# OPC client and subscriber examples in Python on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-Python .
# Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
# a commercial license in order to use Online Forums, and we reply to every post.
# 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='')

Example with time measurement

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.
Rem
Rem Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
Rem OPC client and subscriber examples in VBScript on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VBScript .
Rem Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
Rem a commercial license in order to use Online Forums, and we reply to every post.

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.

.NET

// This example shows how to obtain a data type of all OPC items under a branch.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// OPC client and subscriber examples in C# on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-CSharp .
// Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
// a commercial license in order to use Online Forums, and we reply to every post.

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);
            }
        }
    }
}

Python

# This example shows how to obtain a data type of all OPC items under a branch.
#
# Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
# OPC client and subscriber examples in Python on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-Python .
# Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
# a commercial license in order to use Online Forums, and we reply to every post.
# 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)

OPC XML-DA

Basic Example

.NET

// This example shows how to get value of multiple OPC XML-DA 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.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// OPC client and subscriber examples in C# on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-CSharp .
// Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
// a commercial license in order to use Online Forums, and we reply to every post.

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

namespace DocExamples.DataAccess.Xml
{
    partial class GetMultiplePropertyValues
    {
        public static void Main1Xml()
        {
            // Instantiate the client object.
            var client = new EasyDAClient();

            ServerDescriptor serverDescriptor = "http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx";

            // Get the values of Timestamp and AccessRights properties of two items.
            ValueResult[] results = client.GetMultiplePropertyValues(new[]
            {
                new DAPropertyArguments(serverDescriptor, "Dynamic/Analog Types/Int", DAPropertyDescriptor.Timestamp),
                new DAPropertyArguments(serverDescriptor, "Dynamic/Analog Types/Int", DAPropertyDescriptor.AccessRights),
                new DAPropertyArguments(serverDescriptor, "Static/Analog Types/Double", DAPropertyDescriptor.Timestamp),
                new DAPropertyArguments(serverDescriptor, "Static/Analog Types/Double", 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}");
            }
        }
    }
}

Python

# This example shows how to get value of multiple OPC XML-DA 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.
#
# Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
# OPC client and subscriber examples in Python on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-Python .
# Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
# a commercial license in order to use Online Forums, and we reply to every post.
# 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 *


# Instantiate the client object.
client = EasyDAClient()

serverDescriptor = ServerDescriptor('http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx')

# Get the values of Timestamp and AccessRights properties of two items.
results = client.GetMultiplePropertyValues(
    [
        DAPropertyArguments(serverDescriptor, DANodeDescriptor('Dynamic/Analog Types/Int'), DAPropertyDescriptor.Timestamp),
        DAPropertyArguments(serverDescriptor, DANodeDescriptor('Dynamic/Analog Types/Int'), DAPropertyDescriptor.AccessRights),
        DAPropertyArguments(serverDescriptor, DANodeDescriptor('Static/Analog Types/Double'), DAPropertyDescriptor.Timestamp),
        DAPropertyArguments(serverDescriptor, DANodeDescriptor('Static/Analog Types/Double'), DAPropertyDescriptor.AccessRights)
    ])

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

Example combined with item browsing

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

.NET

// This example shows how to obtain a data type of all OPC XML-DA items under a branch.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// OPC client and subscriber examples in C# on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-CSharp .
// Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
// a commercial license in order to use Online Forums, and we reply to every post.

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.Xml
{
    partial class GetMultiplePropertyValues
    {
        public static void DataTypeXml()
        {
            // Instantiate the client object.
            var client = new EasyDAClient();

            ServerDescriptor serverDescriptor = "http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx";

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

            // 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);
            }
        }
    }
}

COM

// This example shows how to obtain a data type of all OPC XML-DA items under a branch.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// OPC client and subscriber examples in Object Pascal (Delphi) on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-OP .
// Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
// a commercial license in order to use Online Forums, and we reply to every post.

class procedure GetMultiplePropertyValues.DataTypeXml;
var
  Arguments: OleVariant;
  BrowseParameters: _DABrowseParameters;
  Client: OpcLabs_EasyOpcClassic_TLB._EasyDAClient;
  Count: Cardinal;
  Element: OleVariant;
  I: Cardinal;
  PropertyArguments: _DAPropertyArguments;
  ServerDescriptor: _ServerDescriptor;
  NodeDescriptor: _DANodeDescriptor;
//  NodeDescriptorArray: Array of DANodeDescriptor;
  NodeElement: _DANodeElement;
  NodeElementCollection: _DANodeElementCollection;
  NodeElementEnumerator: IEnumVariant;
  ValueResult: _ValueResult;
  ValueResultArray: OleVariant;
  VarType: _VarType;
begin
  ServerDescriptor := CoServerDescriptor.Create;
  ServerDescriptor.UrlString := 'http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx';

  NodeDescriptor := CoDANodeDescriptor.Create;
  NodeDescriptor.ItemId := 'Static/Analog Types';

  BrowseParameters := CoDABrowseParameters.Create;
  BrowseParameters.BrowseFilter := DABrowseFilter_Leaves;

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

  // Browse for all leaves under the "Static/Analog Types" branch
  NodeElementCollection := Client.BrowseNodes(
      ServerDescriptor,
      NodeDescriptor,
      BrowseParameters);


  // Create list of node descriptors, one for aeach leaf obtained
  I := 0;
  Arguments := VarArrayCreate([0, NodeElementCollection.Count - 1], varVariant);
  NodeElementEnumerator := NodeElementCollection.GetEnumerator;
  while (NodeElementEnumerator.Next(1, Element, Count) = S_OK) do
  begin
    NodeElement := IUnknown(Element) as _DANodeElement;
    // filter out hint leafs that do not represent real OPC XML-DA items (rare)
    if Not NodeElement.IsHint then
    begin
      PropertyArguments := CoDAPropertyArguments.Create;
      PropertyArguments.ServerDescriptor := ServerDescriptor;
      PropertyArguments.NodeDescriptor := NodeElement.ToDANodeDescriptor;
      PropertyArguments.PropertyDescriptor.PropertyId.InternalValue := DAPropertyIds_DataType;
      Arguments[I] := PropertyArguments;
      I := I + 1;
    end;
  end;
//  SetLength(Arguments, I);

  // Get the value of DataType property; it is a 16-bit signed integer
  TVarData(ValueResultArray).VType := varArray or varVariant;
  TVarData(ValueResultArray).VArray := PVarArray(
    Client.GetMultiplePropertyValues(Arguments));

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

      // Convert the data type to VarType
      VarType := CoVarType.Create;
      VarType.InternalValue := ValueResult.Value;

      // Display the obtained data type
      WriteLn(Format('s: s', [Arguments[I].NodeDescriptor.NodeId, VarType.ToString]));
  end;
  VarClear(ValueResultArray);
  VarClear(Arguments);
end;

Python

# This example shows how to obtain a data type of all OPC XML-DA items under a branch.
#
# Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
# OPC client and subscriber examples in Python on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-Python .
# Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
# a commercial license in order to use Online Forums, and we reply to every post.
# 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('http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx')

# Instantiate the client object.
client = EasyDAClient()

# Browse for all leaves under the "Static/Analog Types" branch
try:
    nodeElementCollection = IEasyDAClientExtension.BrowseLeaves(client,
                                                                serverDescriptor,
                                                                DANodeDescriptor('Static/Analog Types'))
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)

print()
print('Finished')

 

QuickOPC supports OPC XML-DA also on Linux and macOS.
See Also

Examples - Client OPC Data Access

Examples - Client OPC XML-DA

Examples - Client OPC DA Layered Extensions