GetDataTypePropertyValue(IEasyDAClient,String,String,String) Method

Obtains value of Item Canonical DataType OPC property for a given OPC item.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
<ExtensionAttribute()>
<NotNullAttribute()>
Public Overloads Shared Function GetDataTypePropertyValue( _
   ByVal client As IEasyDAClient, _
   ByVal machineName As String, _
   ByVal serverClass As String, _
   ByVal itemId As String _
) As VarType

'Usage
 
Dim client As IEasyDAClient
Dim machineName As String
Dim serverClass As String
Dim itemId As String
Dim value As VarType
 
value = IEasyDAClientExtension2.GetDataTypePropertyValue(client, machineName, serverClass, itemId)

[Extension()]
[NotNull()]
public static VarType GetDataTypePropertyValue( 
   IEasyDAClient client,
   string machineName,
   string serverClass,
   string itemId
)

[Extension()]
[NotNull()]
public:
static VarType^ GetDataTypePropertyValue( 
   IEasyDAClient^ client,
   String^ machineName,
   String^ serverClass,
   String^ itemId
)

Parameters

client: The client object that will perform the operation.
machineName: Name of the machine. Determines the computer on which the OPC server is located. 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.
serverClass: Contains ProgID of the OPC server to read from.
itemId: Contains OPC item identifier.

Return Value

Returns a value of this OPC property for a specified OPC item, converted to a proper type.

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.

Example

// This example shows how to obtain a data type of an OPC item.

using System;
using OpcLabs.BaseLib.ComInterop;
using OpcLabs.EasyOpc.DataAccess;
using OpcLabs.EasyOpc.DataAccess.Extensions;
using OpcLabs.EasyOpc.OperationModel;

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

            // Get the DataType property value, already converted to VarType
            VarType varType;
            try
            {
                varType = client.GetDataTypePropertyValue("", "OPCLabs.KitServer.2", "Simulation.Random");
            }
            catch (OpcException opcException)
            {
                Console.WriteLine("*** Failure: {0}", opcException.GetBaseException().Message);
                return;
            }

            // Display the obtained data type
            Console.WriteLine("VarType: {0}", varType); // Display data type symbolically
        }
    }
}

# This example shows how to obtain a data type of an OPC item.

# 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.DataAccess.Extensions import *
from OpcLabs.EasyOpc.OperationModel import *


# Instantiate the client object.
client = EasyDAClient()

# Get the DataType property value, already converted to VarType.
try:
    varType = IEasyDAClientExtension2.GetDataTypePropertyValue(client, '', 'OPCLabs.KitServer.2', 'Simulation.Random')
except OpcException as opcException:
    print('*** Failure: ' + opcException.GetBaseException().Message)
    exit()

# Display the obtained data type.
print('VarType: ', varType, sep='')     # Display data type symbolically

print('Finished.')

' This example shows how to obtain a data type of an OPC item.

Imports OpcLabs.BaseLib.ComInterop
Imports OpcLabs.EasyOpc.DataAccess
Imports OpcLabs.EasyOpc.DataAccess.Extensions
Imports OpcLabs.EasyOpc.OperationModel

Namespace DataAccess._EasyDAClientExtension
    Friend Class GetDataTypePropertyValue
        Public Shared Sub Main1()
            Dim client = New EasyDAClient()

            ' Get the DataType property value, already converted to VarType
            Dim varType As VarType
            Try
                varType = client.GetDataTypePropertyValue("", "OPCLabs.KitServer.2", "Simulation.Random")
            Catch opcException As OpcException
                Console.WriteLine("*** Failure: {0}", opcException.GetBaseException().Message)
                Exit Sub
            End Try

            ' Display the obtained data type
            Console.WriteLine("VarType: {0}", varType) ' Display data type symbolically
        End Sub
    End Class
End Namespace

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

IEasyDAClientExtension2 Class
IEasyDAClientExtension2 Members
Overload List

Send Documentation Feedback. Resources: Knowledge Base. Technical support: Online Forums, FAQ.