UAReadArguments Constructor(UAEndpointDescriptor,UANodeDescriptor,UAReadParameters)

Initializes a new instance of the class, specifying the endpoint descriptor, node descriptor, and read parameters.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
Public Function New( _
   ByVal endpointDescriptor As UAEndpointDescriptor, _
   ByVal nodeDescriptor As UANodeDescriptor, _
   ByVal readParameters As UAReadParameters _
)

'Usage
 
Dim endpointDescriptor As UAEndpointDescriptor
Dim nodeDescriptor As UANodeDescriptor
Dim readParameters As UAReadParameters
 
Dim instance As New UAReadArguments(endpointDescriptor, nodeDescriptor, readParameters)

public UAReadArguments( 
   UAEndpointDescriptor endpointDescriptor,
   UANodeDescriptor nodeDescriptor,
   UAReadParameters readParameters
)

public:
UAReadArguments( 
   UAEndpointDescriptor^ endpointDescriptor,
   UANodeDescriptor^ nodeDescriptor,
   UAReadParameters^ readParameters
)

Parameters

endpointDescriptor

Endpoint descriptor. Identifies the OPC-UA server.

Because the OpcLabs.EasyOpc.UA.UAEndpointDescriptor has implicit conversions from System.String and System.Uri, in languages that support implicit conversion operators (such as C# or VB.NET), you can simply use a string (representing the endpoint URL, or a so-called OPC UA endpoint descriptor string), or a System.Uri object, in place of this parameter, and the corresponding endpoint descriptor will be constructed automatically. When the implicit conversion operators are not supported (such as with Python.NET), you can use the OpcLabs.EasyOpc.UA.UAEndpointDescriptor.FromString or OpcLabs.EasyOpc.UA.UAEndpointDescriptor.FromUri static method instead.

If you are using OPC Wizard (for server development), an implicit conversion from OpcLabs.EasyOpc.UA.EasyUAServerCore can be used in the same way to simply pass the server object in place of this parameter, which will use its OpcLabs.EasyOpc.UA.EasyUAServerCore.EffectiveServerDescriptor property for the connection.

The value of this parameter cannot be null (Nothing in Visual Basic).

nodeDescriptor

Node descriptor. Identifies the node in OPC server's address space.

Because the OpcLabs.EasyOpc.UA.UANodeDescriptor has implicit conversions from OpcLabs.EasyOpc.UA.AddressSpace.UANodeId, OpcLabs.EasyOpc.UA.AddressSpace.UANodeElement, OpcLabs.EasyOpc.UA.Navigation.UABrowsePath and System.String, in languages that support implicit conversion operators (such as C# or VB.NET), you can simply use a OpcLabs.EasyOpc.UA.AddressSpace.UANodeId object (representing the Id of the OPC UA node), a node element object (from OPC UA browsing), OpcLabs.EasyOpc.UA.Navigation.UABrowsePath object (representing OPC UA absolute browse path), or a string (with expanded node Id text) in place of this parameter, and the corresponding node descriptor will be constructed automatically. When the implicit conversion operators are not supported (such as with Python.NET), you can use the OpcLabs.EasyOpc.UA.UANodeDescriptor.FromString, OpcLabs.EasyOpc.UA.UANodeDescriptor.FromUABrowsePath, OpcLabs.EasyOpc.UA.UANodeDescriptor.FromUANodeElement or OpcLabs.EasyOpc.UA.UANodeDescriptor.FromUANodeId static method instead.

If you are using OPC Wizard (for server development), an implicit conversion from OpcLabs.EasyOpc.UA.NodeSpace.UAServerNode can be used in the same way to simply pass the server node in place of this parameter, which will use its OpcLabs.EasyOpc.UA.NodeSpace.UAServerNode.EffectiveNodeDescriptor property for the operation.

The value of this parameter cannot be null (Nothing in Visual Basic).

readParameters

Contains parameters for OPC-UA read operations, such as the maximum age of the value.

Because the OpcLabs.EasyOpc.UA.UAReadParameters has implicit conversions from System.Double and OpcLabs.EasyOpc.UA.AddressSpace.UAQualifiedName, in languages that support implicit conversion operators (such as C# or VB.NET), you can simply use a double precision floating point number (representing the maximum value age in milliseconds), or an OPC UA qualified name (representing the name of the encoding to be used) in place of this parameter, and the corresponding OPC UA read parameters will be constructed automatically. When the implicit conversion operators are not supported (such as with Python.NET), you can use the OpcLabs.EasyOpc.UA.UAReadParameters.FromDouble or OpcLabs.EasyOpc.UA.UAReadParameters.FromUAQualifiedName static method instead.

The value of this parameter cannot be null (Nothing in Visual Basic).

Exceptions

Exception Description

Exception	Description
System.ArgumentNullException	A `null` reference (`Nothing` in Visual Basic) is passed to a method that does not accept it as a valid argument. This is a usage error, i.e. it will never occur (the exception will not be thrown) in a correctly written program. Your code should not catch this exception.

System.ArgumentNullException

A null reference (Nothing in Visual Basic) is passed to a method that does not accept it as a valid argument.

This is a usage error, i.e. it will never occur (the exception will not be thrown) in a correctly written program. Your code should not catch this exception.

Remarks

You can obtain nodeDescriptor e.g. by calling one of the browsing methods on OpcLabs.EasyOpc.UA.EasyUAClientCore object.

Example

CSharp
VB.NET
Python

// This example shows how to read data value of 3 nodes at once, from the device (data source).
//
// 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.UA;
using OpcLabs.EasyOpc.UA.OperationModel;

namespace UADocExamples._EasyUAClient
{
    partial class ReadMultiple
    {
        public static void FromDevice()
        {
            UAEndpointDescriptor endpointDescriptor =
                "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer";
            // or "http://opcua.demo-this.com:51211/UA/SampleServer" (currently not supported)
            // or "https://opcua.demo-this.com:51212/UA/SampleServer/"

            // Instantiate the client object
            var client = new EasyUAClient();

            // Obtain attribute data. By default, the Value attributes of the nodes will be read.
            // The parameters specify reading from the device (data source), which may be slow but provides the very latest
            // data.
            UAAttributeDataResult[] attributeDataResultArray = client.ReadMultiple(new[]
                {
                    new UAReadArguments(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10845", 
                        UAReadParameters.FromDevice),
                    new UAReadArguments(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10853", 
                        UAReadParameters.FromDevice),
                    new UAReadArguments(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10855", 
                        UAReadParameters.FromDevice)
                });

            // Display results
            foreach (UAAttributeDataResult attributeDataResult in attributeDataResultArray)
            {
                if (attributeDataResult.Succeeded)
                    Console.WriteLine("AttributeData: {0}", attributeDataResult.AttributeData);
                else
                    Console.WriteLine("*** Failure: {0}", attributeDataResult.ErrorMessageBrief);
            }
        }

        // Example output:
        //
        //AttributeData: 51 {System.Int16} @11/6/2011 1:49:19 PM @11/6/2011 1:49:19 PM; Good
        //AttributeData: -1993984 {System.Single} @11/6/2011 1:49:19 PM @11/6/2011 1:49:19 PM; Good
        //AttributeData: Yellow% Dragon Cat) White Blue Dog# Green Banana- {System.String} @11/6/2011 1:49:19 PM @11/6/2011 1:49:19 PM; Good            
    }
}

' This example shows how to read data value of 3 nodes at once, from the device (data source).
'
' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
' OPC client and subscriber examples in VB.NET on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VBNET .
' 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.

Imports OpcLabs.EasyOpc.UA
Imports OpcLabs.EasyOpc.UA.OperationModel

Namespace _EasyUAClient
    Partial Friend Class ReadMultiple
        Public Shared Sub FromDevice()

            ' Define which server we will work with.
            Dim endpointDescriptor As UAEndpointDescriptor =
                    "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"
            ' or "http://opcua.demo-this.com:51211/UA/SampleServer" (currently not supported)
            ' or "https://opcua.demo-this.com:51212/UA/SampleServer/"

            ' Instantiate the client object
            Dim client = New EasyUAClient()

            ' Obtain attribute data. By default, the Value attributes of the nodes will be read.
            ' The parameters specify reading from the device (data source), which may be slow but provides the very latest
            ' data.
            Dim attributeDataResultArray() As UAAttributeDataResult = client.ReadMultiple(New UAReadArguments() _
               {
                   New UAReadArguments(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10845",
                        UAReadParameters.FromDevice),
                    New UAReadArguments(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10853",
                        UAReadParameters.FromDevice),
                    New UAReadArguments(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10855",
                        UAReadParameters.FromDevice)
               })

            ' Display results
            For Each attributeDataResult As UAAttributeDataResult In attributeDataResultArray
                If attributeDataResult.Succeeded Then
                    Console.WriteLine("AttributeData: {0}", attributeDataResult.AttributeData)
                Else
                    Console.WriteLine("*** Failure: {0}", attributeDataResult.ErrorMessageBrief)
                End If
            Next attributeDataResult

            ' Example output:
            '
            'AttributeData: 51 {System.Int16} @11/6/2011 1:49:19 PM @11/6/2011 1:49:19 PM; Good
            'AttributeData: -1993984 {System.Single} @11/6/2011 1:49:19 PM @11/6/2011 1:49:19 PM; Good
            'AttributeData: Yellow% Dragon Cat) White Blue Dog# Green Banana- {System.String} @11/6/2011 1:49:19 PM @11/6/2011 1:49:19 PM; Good            
        End Sub
    End Class
End Namespace

# This example shows how to read data value of 3 nodes at once, from the device (data source).
#
# 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 time

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


endpointDescriptor = UAEndpointDescriptor('opc.tcp://opcua.demo-this.com:51210/UA/SampleServer')
# or 'http://opcua.demo-this.com:51211/UA/SampleServer' (currently not supported)
# or 'https://opcua.demo-this.com:51212/UA/SampleServer/'

# Instantiate the client object.
client = EasyUAClient()

# Obtain attribute data. By default, the Value attributes of the nodes will be read.
# The parameters specify reading from the device (data source), which may be slow but provides the very latest
# data.
attributeDataResultArray = client.ReadMultiple([
    UAReadArguments(endpointDescriptor, UANodeDescriptor('nsu=http://test.org/UA/Data/ ;i=10845'),
                    UAReadParameters.FromDevice),
    UAReadArguments(endpointDescriptor, UANodeDescriptor('nsu=http://test.org/UA/Data/ ;i=10853'),
                    UAReadParameters.FromDevice),
    UAReadArguments(endpointDescriptor, UANodeDescriptor('nsu=http://test.org/UA/Data/ ;i=10855'),
                    UAReadParameters.FromDevice),
    ])

# Display results.
for attributeDataResult in attributeDataResultArray:
    if attributeDataResult.Succeeded:
        print('AttributeData: ', attributeDataResult.AttributeData, sep='')
    else:
        print('*** Failure: ', attributeDataResult.ErrorMessageBrief, sep='')

print()
print('Finished.')

Requirements

Target Platforms: .NET Framework: Windows 10 (selected versions), Windows 11 (selected versions), Windows Server 2016, Windows Server 2022; .NET: Linux, macOS, Microsoft Windows

Reference

UAReadArguments Class
UAReadArguments Members
Overload List

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