WriteItem(IEasyDAClient,ServerDescriptor,DAItemDescriptor,DAVtq) Method

Writes DAVtq into a named item using descriptor objects for the OPC server and OPC-DA item.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
<ExtensionAttribute()>
Public Overloads Shared Sub WriteItem( _
   ByVal client As IEasyDAClient, _
   ByVal serverDescriptor As ServerDescriptor, _
   ByVal itemDescriptor As DAItemDescriptor, _
   ByVal vtq As DAVtq _
)

'Usage
 
Dim client As IEasyDAClient
Dim serverDescriptor As ServerDescriptor
Dim itemDescriptor As DAItemDescriptor
Dim vtq As DAVtq
 
IEasyDAClientExtension.WriteItem(client, serverDescriptor, itemDescriptor, vtq)

[Extension()]
public static void WriteItem( 
   IEasyDAClient client,
   ServerDescriptor serverDescriptor,
   DAItemDescriptor itemDescriptor,
   DAVtq vtq
)

[Extension()]
public:
static void WriteItem( 
   IEasyDAClient^ client,
   ServerDescriptor^ serverDescriptor,
   DAItemDescriptor^ itemDescriptor,
   DAVtq^ vtq
)

Parameters

client

The client object that will perform the operation.

This is typically the EasyDAClient object.

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

serverDescriptor

The OPC server involved in the operation.

Because the OpcLabs.EasyOpc.ServerDescriptor has an implicit conversion from System.Guid, System.String and OpcLabs.EasyOpc.ServerElement, in languages that support implicit conversion operators (such as C# or VB.NET), you can simply use a GUID (representing the CLSID of the server), a string (representing the so-called OPC server descriptor string, such as a ProgID or the URL of the server), or a OpcLabs.EasyOpc.ServerElement object (result from OPC browsing), in place of this parameter, and the corresponding OPC server descriptor will be constructed automatically. When the implicit conversion operators are not supported (such as with Python.NET), you can use the FromGuid, FromString or FromServerElement static method instead.

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

itemDescriptor

The OPC item involved in the operation.

Because the DAItemDescriptor has an implicit conversion from System.String and OpcLabs.EasyOpc.DataAccess.AddressSpace.DANodeElement, in languages that support implicit conversion operators (such as C# or VB.NET), you can simply use a string (representing the qualified name of the node), or a OpcLabs.EasyOpc.DataAccess.AddressSpace.DANodeElement object (result from OPC browsing), in place of this parameter, and the corresponding OPC DA item descriptor will be constructed automatically. When the implicit conversion operators are not supported (such as with Python.NET), you can use the FromString or FromDANodeElement static method instead.

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

vtq

The object containing the value, timestamp and quality to be written.

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.
OpcLabs.EasyOpc.OperationModel.OpcException	The OPC "Classic" (or OPC XML-DA) operation has failed. This operation exception in uniformly used to allow common handling of various kinds of errors. The System.Exception.InnerException always contains information about the actual error cause. This is an operation error that depends on factors external to your program, and thus cannot be always avoided. Your code must handle it appropriately.

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.

OpcLabs.EasyOpc.OperationModel.OpcException

The OPC "Classic" (or OPC XML-DA) operation has failed. This operation exception in uniformly used to allow common handling of various kinds of errors. The System.Exception.InnerException always contains information about the actual error cause.

This is an operation error that depends on factors external to your program, and thus cannot be always avoided. Your code must handle it appropriately.

Remarks

The server(s) can be local or can be remotely accessed via DCOM.

Optionally, a specific data type can be requested, or an access path can be specified (OPC DA 1.0 only).

This is an extension method (info: C#, VB.NET). In languages that have support for extensions methods (such as C# and VB.NET), you can use the extension method as if it were a regular method on the object that is its first parameter. In other languages (such as with Python.NET), you will call the extension as a static method, and pass it the object on which it acts as its first parameter.

Example

CSharp
VB.NET
Object Pascal
VBScript
Python

// This example shows how to write a value, timestamp and quality into a single 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.EasyOpc.DataAccess;
using OpcLabs.EasyOpc.OperationModel;

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

            try
            {
                client.WriteItem("", "OPCLabs.KitServer.2", "Simulation.Register_I4", 
                    12345, DateTime.SpecifyKind(new DateTime(1980, 1, 1), DateTimeKind.Utc), 192);
            }
            catch (OpcException opcException)
            {
                Console.WriteLine($"*** Failure: {opcException.GetBaseException().Message}");
                return;
            }
            Console.WriteLine("Success");
        }
    }
}

' This example shows how to write a value, timestamp and quality into a single item.
'
' 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 WriteItem
        Public Shared Sub Main1()
            ' Instantiate the client object.
            Dim client = New EasyDAClient()

            Try
                client.WriteItem("", "OPCLabs.KitServer.2", "Simulation.Register_I4",
                    12345, DateTime.SpecifyKind(New DateTime(1980, 1, 1), DateTimeKind.Utc), 192)
            Catch opcException As OpcException
                Console.WriteLine("*** Failure: {0}", opcException.GetBaseException().Message)
                Exit Sub
            End Try
            Console.WriteLine("Success")
        End Sub
    End Class
End Namespace

// This example shows how to write a value, timestamp and quality into a single item.
//
// 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 WriteItem.Main;
var
  Client: OpcLabs_EasyOpcClassic_TLB._EasyDAClient;
begin
  // Instantiate the client object
  Client := CoEasyDAClient.Create;

  try
    Client.WriteItem('', 'OPCLabs.KitServer.2', 'Simulation.Register_I4', 12345, EncodeDate(1980, 1, 1), DAQualities_GoodNonSpecific);
  except
    on E: EOleException do
    begin
      WriteLn(Format('*** Failure: %s', [E.GetBaseException.Message]));
      Exit;
    end;
  end;

end;

Rem This example shows how to write a value, timestamp and quality into a single item.
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 Client: Set Client = CreateObject("OpcLabs.EasyOpc.DataAccess.EasyDAClient")
On Error Resume Next
Client.WriteItem "", "OPCLabs.KitServer.2", "Simulation.Register_I4", 12345, DateSerial(1980, 1, 1), 192
If Err.Number <> 0 Then
    WScript.Echo "*** Failure: " & Err.Source & ": " & Err.Description
    WScript.Quit
End If
On Error Goto 0

# This example shows how to write a value, timestamp and quality into a single 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 System import *
from OpcLabs.EasyOpc.DataAccess import *
from OpcLabs.EasyOpc.OperationModel import *


# Instantiate the client object.
client = EasyDAClient()

# Perform the operation
try:
    IEasyDAClientExtension.WriteItem(client, '', 'OPCLabs.KitServer.2', 'Simulation.Register_I4',
                                     12345, DateTime.SpecifyKind(DateTime(1980, 1, 1), DateTimeKind.Utc),
                                     DAQuality(192))
except OpcException as opcException:
    print('*** Failure: ' + opcException.GetBaseException().Message, sep='')
    exit()

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

IEasyDAClientExtension Class
IEasyDAClientExtension Members
Overload List

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