DAItemGroupArguments Constructor(String,String,String,VarType,Int32,Single,Object)

Initializes a new instance of the class, with the OPC server specified by machine name and server class, the OPC item specified by its ItemId and data type, the OPC group parameters specified by requested update rate and percent deadband, and with a user-defined state object.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
Public Function New( _
   ByVal machineName As String, _
   ByVal serverClass As String, _
   ByVal itemId As String, _
   ByVal dataType As VarType, _
   ByVal requestedUpdateRate As Integer, _
   ByVal percentDeadband As Single, _
   ByVal state As Object _
)

'Usage
 
Dim machineName As String
Dim serverClass As String
Dim itemId As String
Dim dataType As VarType
Dim requestedUpdateRate As Integer
Dim percentDeadband As Single
Dim state As Object
 
Dim instance As New DAItemGroupArguments(machineName, serverClass, itemId, dataType, requestedUpdateRate, percentDeadband, state)

public DAItemGroupArguments( 
   string machineName,
   string serverClass,
   string itemId,
   VarType dataType,
   int requestedUpdateRate,
   float percentDeadband,
   object state
)

public:
DAItemGroupArguments( 
   String^ machineName,
   String^ serverClass,
   String^ itemId,
   VarType^ dataType,
   int requestedUpdateRate,
   float percentDeadband,
   Object^ state
)

Parameters

machineName

Name of the machine. Determines the computer on which the OPC server is located. It may be an empty string, in which case the OPC server is assumed to exist on the local computer or at the computer specified for it by DCOM configuration.

The value represents a UNC or DNS computer name. Any string can be passed to this parameter (i.e. will not cause System.ArgumentException), but not all values make sense and will work when an operation using them is attempted. IPv6 addresses are normally enclosed between '[' and ']'.

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

serverClass

Contains ProgID of the OPC server.

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

itemId

Contains OPC item identifier.

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

dataType

Specifies the data type requested. Passing OpcLabs.BaseLib.ComInterop.VarTypes.Empty means that the server's canonical data type should be used.

Because the OpcLabs.BaseLib.ComInterop.VarType has an implicit conversion from System.Int32 and OpcLabs.BaseLib.ComInterop.VarTypes, in languages that support implicit conversion operators (such as C# or VB.NET), you can simply use an integer (representing the numerical value of the COM VARTYPE), or an element of the OpcLabs.BaseLib.ComInterop.VarTypes enumeration (or an allowed combination of OpcLabs.BaseLib.ComInterop.VarTypes flags) in place of this parameter, and the corresponding data type specification will be constructed automatically. When the implicit conversion operators are not supported (such as with Python.NET), you can use the OpcLabs.BaseLib.ComInterop.VarType.VarType Constructor(Int32) or OpcLabs.BaseLib.ComInterop.VarType.VarType Constructor(VarTypes) constructor instead.

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

requestedUpdateRate

How often should the updates be received (number of milliseconds).

percentDeadband

The percent change in an item value that will cause an update.

state

The state object (can be any value supplied by your code); available in event notifications.

The value of this parameter can be null (Nothing in Visual Basic).

Exceptions

Exception Description

Exception	Description
System.ArgumentException	One of the arguments provided to a method is not valid. 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.
System.ArgumentOutOfRangeException	The value of an argument is outside the allowable range of values as defined by the invoked method. 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.ArgumentException

One of the arguments provided to a method is not valid.

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.

System.ArgumentOutOfRangeException

The value of an argument is outside the allowable range of values as defined by the invoked method.

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.

Example

CSharp
VB.NET
Python

// This example shows how subscribe to changes of multiple items with percent deadband.
//
// 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.Threading;
using OpcLabs.BaseLib.ComInterop;
using OpcLabs.EasyOpc.DataAccess;
using OpcLabs.EasyOpc.DataAccess.OperationModel;

namespace DocExamples.DataAccess._EasyDAClient
{
    partial class SubscribeMultipleItems
    {
        public static void PercentDeadband()
        {
            // Instantiate the client object.
            using (var client = new EasyDAClient())
            {
                client.ItemChanged += client_PercentDeadband_ItemChanged;

                Console.WriteLine("Subscribing with different percent deadbands...");
                client.SubscribeMultipleItems(
                    new[] {
                            new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Ramp 0:100 (10 s)", 
                                VarTypes.Empty, requestedUpdateRate:100, percentDeadband:10.0f, null), 
                            new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Ramp 0:100 (1 min)",
                                VarTypes.Empty, requestedUpdateRate:100, percentDeadband:5.0f, null),
                        });

                Console.WriteLine("Processing item changed events for 1 minute...");
                Thread.Sleep(60 * 1000);
            }
        }

        // Item changed event handler
        static void client_PercentDeadband_ItemChanged(object sender, EasyDAItemChangedEventArgs e)
        {
            if (e.Succeeded)
                Console.WriteLine("{0}: {1}", e.Arguments.ItemDescriptor.ItemId, e.Vtq);
            else
                Console.WriteLine("{0} *** Failure: {1}", e.Arguments.ItemDescriptor.ItemId, e.ErrorMessageBrief);
        }
    }
}

' This example shows how subscribe to changes of multiple items with percent deadband.
'
' 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 System.Threading
Imports OpcLabs.BaseLib.ComInterop
Imports OpcLabs.EasyOpc.DataAccess
Imports OpcLabs.EasyOpc.DataAccess.OperationModel

Namespace DataAccess._EasyDAClient
    Partial Friend Class SubscribeMultipleItems
        Public Shared Sub PercentDeadband()
            ' Instantiate the client object.
            Using client = New EasyDAClient()
                AddHandler client.ItemChanged, AddressOf client_PercentDeadband_ItemChanged

                Console.WriteLine("Subscribing with different percent deadbands...")
                client.SubscribeMultipleItems(New DAItemGroupArguments() {
                    New DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Ramp 0:100 (10 s)",
                        VarTypes.Empty, requestedUpdateRate:=100, percentDeadband:=10.0F, Nothing),
                    New DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Ramp 0:100 (1 min)",
                        VarTypes.Empty, requestedUpdateRate:=100, percentDeadband:=5.0F, Nothing)
                    })

                Console.WriteLine("Processing item changed events for 1 minute...")
                Thread.Sleep(60 * 1000)
            End Using
        End Sub

        ' Item changed event handler
        Private Shared Sub client_PercentDeadband_ItemChanged(ByVal sender As Object, ByVal e As EasyDAItemChangedEventArgs)
            If e.Succeeded Then
                Console.WriteLine("{0}: {1}", e.Arguments.ItemDescriptor.ItemId, e.Vtq)
            Else
                Console.WriteLine("{0} *** Failure: {1}", e.Arguments.ItemDescriptor.ItemId, e.ErrorMessageBrief)
            End If
        End Sub
    End Class
End Namespace

# This example shows how subscribe to changes of multiple items with percent deadband.
#
# 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.BaseLib.ComInterop import *
from OpcLabs.EasyOpc.DataAccess import *
from OpcLabs.EasyOpc.DataAccess.OperationModel import *


# Item changed event handler.
def itemChanged(sender, e):
    if e.Succeeded:
        print(e.Arguments.ItemDescriptor.ItemId, ': ', e.Vtq, sep='')
    else:
        print(e.Arguments.ItemDescriptor.ItemId, ' *** Failure: ', e.ErrorMessageBrief, sep='')


# Instantiate the client object.
client = EasyDAClient()

client.ItemChanged += itemChanged

print('Subscribing item changes with different percent deadbands...')
IEasyDAClientExtension.SubscribeMultipleItems(client, [
    DAItemGroupArguments('', 'OPCLabs.KitServer.2', 'Simulation.Ramp 0:100 (10 s)',
                         VarType(VarTypes.Empty), 100, 10.0, None),
    DAItemGroupArguments('', 'OPCLabs.KitServer.2', 'Simulation.Ramp 0:100 (1 min)',
                         VarType(VarTypes.Empty), 100, 5.0, None),
    ])

print('Processing item change notifications for 1 minute...')
time.sleep(60)

print('Unsubscribing all items...')
client.UnsubscribeAllItems()

client.ItemChanged -= itemChanged

print('Finished.')

CSharp
VB.NET
Python

// This example shows how subscribe to changes of multiple items with percent deadband.
//
// 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.Threading;
using OpcLabs.BaseLib.ComInterop;
using OpcLabs.EasyOpc;
using OpcLabs.EasyOpc.DataAccess;
using OpcLabs.EasyOpc.DataAccess.OperationModel;

namespace DocExamples.DataAccess.Xml
{
    partial class SubscribeMultipleItems
    {
        public static void PercentDeadbandXml()
        {
            // Instantiate the client object.
            using (var client = new EasyDAClient())
            {
                client.ItemChanged += client_PercentDeadband_ItemChanged;

                Console.WriteLine("Subscribing with different percent deadbands...");
                client.SubscribeMultipleItems(
                    new[] {
                            new DAItemGroupArguments("http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx", new DAItemDescriptor("Dynamic/Analog Types/Int", 
                                VarTypes.Empty), new DAGroupParameters(requestedUpdateRate:100, percentDeadband:10.0f), null), 
                            new DAItemGroupArguments("http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx", new DAItemDescriptor("Dynamic/Analog Types/Double",
                                VarTypes.Empty), new DAGroupParameters(requestedUpdateRate:100, percentDeadband:5.0f), null),
                        });

                Console.WriteLine("Processing item changed events for 1 minute...");
                Thread.Sleep(60 * 1000);
            }
        }

        // Item changed event handler
        static void client_PercentDeadband_ItemChanged(object sender, EasyDAItemChangedEventArgs e)
        {
            if (e.Succeeded)
                Console.WriteLine("{0}: {1}", e.Arguments.ItemDescriptor.ItemId, e.Vtq);
            else
                Console.WriteLine("{0} *** Failure: {1}", e.Arguments.ItemDescriptor.ItemId, e.ErrorMessageBrief);
        }
    }
}

' This example shows how subscribe to changes of multiple items with percent deadband.
'
' 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 System.Threading
Imports OpcLabs.BaseLib.ComInterop
Imports OpcLabs.EasyOpc.DataAccess
Imports OpcLabs.EasyOpc.DataAccess.OperationModel

Namespace DataAccess.Xml
    Partial Friend Class SubscribeMultipleItems
        Public Shared Sub PercentDeadbandXml()
            ' Instantiate the client object.
            Using client = New EasyDAClient()
                AddHandler client.ItemChanged, AddressOf client_PercentDeadband_ItemChanged

                Console.WriteLine("Subscribing with different percent deadbands...")
                client.SubscribeMultipleItems(New DAItemGroupArguments() {
                    New DAItemGroupArguments("http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx", New DAItemDescriptor("Dynamic/Analog Types/Int",
                                VarTypes.Empty), New DAGroupParameters(requestedUpdateRate:=100, percentDeadband:=10.0F), Nothing),
                    New DAItemGroupArguments("http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx", New DAItemDescriptor("Dynamic/Analog Types/Double",
                                VarTypes.Empty), New DAGroupParameters(requestedUpdateRate:=100, percentDeadband:=5.0F), Nothing)
                    })

                Console.WriteLine("Processing item changed events for 1 minute...")
                Thread.Sleep(60 * 1000)
            End Using
        End Sub

        ' Item changed event handler
        Private Shared Sub client_PercentDeadband_ItemChanged(ByVal sender As Object, ByVal e As EasyDAItemChangedEventArgs)
            If e.Succeeded Then
                Console.WriteLine("{0}: {1}", e.Arguments.ItemDescriptor.ItemId, e.Vtq)
            Else
                Console.WriteLine("{0} *** Failure: {1}", e.Arguments.ItemDescriptor.ItemId, e.ErrorMessageBrief)
            End If
        End Sub
    End Class
End Namespace

# This example shows how subscribe to changes of multiple items with percent deadband.
#
# 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.BaseLib.ComInterop import *
from OpcLabs.EasyOpc import *
from OpcLabs.EasyOpc.DataAccess import *
from OpcLabs.EasyOpc.DataAccess.OperationModel import *


# Item changed event handler
def itemChanged(sender, e):
    if e.Succeeded:
        print(e.Arguments.ItemDescriptor.ItemId, ': ', e.Vtq, sep='')
    else:
        print(e.Arguments.ItemDescriptor.ItemId, ' *** Failure: ', e.ErrorMessageBrief, sep='')


# Instantiate the client object
client = EasyDAClient()
client.ItemChanged += itemChanged

print('Subscribing with different percent deadbands...')
IEasyDAClientExtension.SubscribeMultipleItems(client,
    [
        DAItemGroupArguments(
            ServerDescriptor('http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx'),
            DAItemDescriptor('Dynamic/Analog Types/Int', VarType(VarTypes.Empty)),
            DAGroupParameters(100, 10.0),
            None),
        DAItemGroupArguments(
            ServerDescriptor('http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx'),
            DAItemDescriptor('Dynamic/Analog Types/Double', VarType(VarTypes.Empty)),
            DAGroupParameters(100, 5.0),
            None),
    ])

print('Processing item change notifications for 1 minute...')
time.sleep(60)

print('Unsubscribing all items...')
client.UnsubscribeAllItems()

client.ItemChanged -= itemChanged

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

DAItemGroupArguments Class
DAItemGroupArguments Members
Overload List

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