Examples - OPC Data Access - Read an item synchronously

C#
VB.NET

// This example shows how to read an item synchronously, and display its value, timestamp and quality.
//
// 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 ReadItem
    {
        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;

            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 an item synchronously, and display its value, timestamp and quality.
'
' 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.DataAccess
Imports OpcLabs.EasyOpc.OperationModel

Namespace DataAccess._EasyDAClient
Partial Friend Class ReadItem
Public Shared Sub Synchronous()
' Instantiate the client object.
Dim 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

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

Python

Python (.NET)

# This example shows how to read an item synchronously, and display its value, timestamp and quality.
#
# 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.OperationModel import *


# Instantiate the client object.
client = 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

# Perform the operation.
try:
    vtq = IEasyDAClientExtension.ReadItem(client, '', 'OPCLabs.KitServer.2', 'Simulation.Random')
except OpcException as opcException:
    print('*** Failure: ' + opcException.GetBaseException().Message, sep='')
    exit()

# Display results.
print('Vtq: ', vtq, sep='')

Python

Concepts

Examples - Client OPC Unified Architecture

Examples - Client OPC DA Layered Extensions