Examples - OPC Data Access - Read a single item

.NET

// 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 "../../../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

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.

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

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


# Instantiate the client object.
client = EasyDAClient()

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

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

' 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 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

COM

// 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.

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

.NET

COM

Conceptual

Examples - OPC Unified Architecture

Examples - OPC DA Layered Extensions