WriteItemValue(IEasyDAClient,String,String,String,Object,VarType) Method

Writes a value into a named item using individual parameters specifying its location, and a specific data type.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
<ExtensionAttribute()>
Public Overloads Shared Sub WriteItemValue( _
   ByVal client As IEasyDAClient, _
   ByVal machineName As String, _
   ByVal serverClass As String, _
   ByVal itemId As String, _
   ByVal value As Object, _
   ByVal dataType As VarType _
)

'Usage
 
Dim client As IEasyDAClient
Dim machineName As String
Dim serverClass As String
Dim itemId As String
Dim value As Object
Dim dataType As VarType
 
IEasyDAClientExtension.WriteItemValue(client, machineName, serverClass, itemId, value, dataType)

[Extension()]
public static void WriteItemValue( 
   IEasyDAClient client,
   string machineName,
   string serverClass,
   string itemId,
   object value,
   VarType dataType
)

[Extension()]
public:
static void WriteItemValue( 
   IEasyDAClient^ client,
   String^ machineName,
   String^ serverClass,
   String^ itemId,
   Object^ value,
   VarType^ dataType
)

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).

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 to write into.

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).

value

The value to be written.

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

dataType

Specifies the data type. Passing OpcLabs.BaseLib.ComInterop.VarTypes.Empty will cause the value be written using server's canonical data type.

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).

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.
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.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.

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

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
Python

// This example shows how to write a value into a single item, specifying its requested data type.
//
// Find all latest examples here: https://www.doc-that.com/files/onlinedocs/OPCLabs-ConnectivityStudio/Latest/examples.html .
// OPC client and subscriber examples in C# on GitHub: https://github.com/OPCLabs/Examples-ConnectivityStudio-CSharp .
// Missing some example? Ask us for it on our Online Forums, https://forum.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.BaseLib.ComInterop;
using OpcLabs.EasyOpc.DataAccess;
using OpcLabs.EasyOpc.OperationModel;

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

            try
            {
                client.WriteItemValue("", "OPCLabs.KitServer.2", "Simulation.Register_I4", 12345,
                    VarTypes.I4);   // <-- the requested data type
            }
            catch (OpcException opcException)
            {
                Console.WriteLine("*** Failure: {0}", opcException.GetBaseException().Message);
            }
        }
    }
}

' This example shows how to write a value into a single item, specifying its requested data type.
'
' Find all latest examples here: https://www.doc-that.com/files/onlinedocs/OPCLabs-ConnectivityStudio/Latest/examples.html .
' OPC client and subscriber examples in VB.NET on GitHub: https://github.com/OPCLabs/Examples-ConnectivityStudio-VBNET .
' Missing some example? Ask us for it on our Online Forums, https://forum.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.BaseLib.ComInterop
Imports OpcLabs.EasyOpc.DataAccess
Imports OpcLabs.EasyOpc.OperationModel

Namespace Global.DocExamples.DataAccess._EasyDAClient
    Partial Friend Class WriteItemValue
        Public Shared Sub RequestedDataType()
            Dim client = New EasyDAClient()

            Try
                client.WriteItemValue("", "OPCLabs.KitServer.2", "Simulation.Register_I4", 12345,
                                      VarTypes.I4) ' <-- the requested data type
            Catch opcException As OpcException
                Console.WriteLine("*** Failure: {0}", opcException.GetBaseException().Message)
                Exit Sub
            End Try
        End Sub
    End Class
End Namespace

# This example shows how to write a value into a single item, specifying its requested data type.
#
# Find all latest examples here: https://www.doc-that.com/files/onlinedocs/OPCLabs-ConnectivityStudio/Latest/examples.html .
# OPC client and subscriber examples in Python on GitHub: https://github.com/OPCLabs/Examples-ConnectivityStudio-Python .
# Missing some example? Ask us for it on our Online Forums, https://forum.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.BaseLib.ComInterop import *
from OpcLabs.EasyOpc.DataAccess import *
from OpcLabs.EasyOpc.OperationModel import *


# Instantiate the client object.
client = EasyDAClient()

# Perform the operation
try:
    IEasyDAClientExtension.WriteItemValue(client, '', 'OPCLabs.KitServer.2', 'Simulation.Register_I4', 12345,
                                          VarType(VarTypes.I4)) # <-- the requested data type
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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