QuerySourceConditions Method (EasyAEClientCore)

Finds out event conditions associated with the specified source name. Uses server descriptor for specifying the OPC server.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
Public Function QuerySourceConditions( _
   ByVal serverDescriptor As ServerDescriptor, _
   ByVal sourceNodeDescriptor As AENodeDescriptor _
) As AEConditionElementCollection

'Usage
 
Dim instance As EasyAEClientCore
Dim serverDescriptor As ServerDescriptor
Dim sourceNodeDescriptor As AENodeDescriptor
Dim value As AEConditionElementCollection
 
value = instance.QuerySourceConditions(serverDescriptor, sourceNodeDescriptor)

public AEConditionElementCollection QuerySourceConditions( 
   ServerDescriptor serverDescriptor,
   AENodeDescriptor sourceNodeDescriptor
)

public:
AEConditionElementCollection^ QuerySourceConditions( 
   ServerDescriptor^ serverDescriptor,
   AENodeDescriptor^ sourceNodeDescriptor
)

Parameters

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 OpcLabs.EasyOpc.ServerDescriptor.FromGuid, OpcLabs.EasyOpc.ServerDescriptor.FromString or OpcLabs.EasyOpc.ServerDescriptor.FromServerElement static method instead.

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

sourceNodeDescriptor

A source node descriptor, usually expressed as qualified source name. Only the conditions associated with this source are returned.

Because the AENodeDescriptor has an implicit conversion from System.String and OpcLabs.EasyOpc.AlarmsAndEvents.AddressSpace.AENodeElement, 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.AlarmsAndEvents.AddressSpace.AENodeElement object (result from OPC browsing), in place of this parameter, and the corresponding OPC A&E node descriptor will be constructed automatically. When the implicit conversion operators are not supported (such as with Python.NET), you can use the AENodeDescriptor.FromString or AENodeDescriptor.FromAENodeElement static method instead.

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

Return Value

A collection of condition elements, one element for each condition of the given source.

This method never returns null (Nothing in Visual Basic).

The individual elements of the returned value are never 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.

Example

CSharp
VB.NET
Python

// This example shows how to enumerate all event conditions associated with the specified event source.
//
// 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.Diagnostics;
using OpcLabs.EasyOpc.AlarmsAndEvents;
using OpcLabs.EasyOpc.AlarmsAndEvents.AddressSpace;
using OpcLabs.EasyOpc.OperationModel;

namespace DocExamples.AlarmsAndEvents._EasyAEClient
{
    class QuerySourceConditions 
    { 
        public static void Main1()
        {
            // Instantiate the client object.
            var client = new EasyAEClient();

            AEConditionElementCollection conditionElements;
            try
            {
                conditionElements = client.QuerySourceConditions("", "OPCLabs.KitEventServer.2", 
                    "Simulation.ConditionState1");
            }
            catch (OpcException opcException)
            {
                Console.WriteLine("*** Failure: {0}", opcException.GetBaseException().Message);
                return;
            }

            foreach (AEConditionElement conditionElement in conditionElements)
            {
                Debug.Assert(conditionElement != null);
                Console.WriteLine("ConditionElements[\"{0}\"]: {1} subcondition(s)", 
                    conditionElement.Name, conditionElement.SubconditionNames.Length);
            }
        }
    } 
}

' This example shows how to enumerate all event conditions associated with the specified event source.
'
' 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.AlarmsAndEvents
Imports OpcLabs.EasyOpc.AlarmsAndEvents.AddressSpace
Imports OpcLabs.EasyOpc.OperationModel

Namespace AlarmsAndEvents._EasyAEClient

    Friend Class QuerySourceConditions
        Public Shared Sub Main1()
            Dim client = New EasyAEClient()

            Dim conditionElements As AEConditionElementCollection
            Try
                conditionElements = client.QuerySourceConditions( _
                    "", "OPCLabs.KitEventServer.2", "Simulation.ConditionState1")
            Catch opcException As OpcException
                Console.WriteLine("*** Failure: {0}", opcException.GetBaseException().Message)
                Exit Sub
            End Try

            For Each conditionElement As AEConditionElement In conditionElements
                Debug.Assert(conditionElement IsNot Nothing)
                Console.WriteLine("ConditionElements[""{0}""]: {1} subcondition(s)", _
                                  conditionElement.Name, conditionElement.SubconditionNames.Length)
            Next conditionElement
        End Sub
    End Class

End Namespace

# This example shows how to enumerate all event conditions associated with the specified event source.
#
# 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 OpcLabs.EasyOpc import *
from OpcLabs.EasyOpc.AlarmsAndEvents import *
from OpcLabs.EasyOpc.OperationModel import *


# Instantiate the client object.
client = EasyAEClient()

# Perform the operation.
try:
    conditionElements = IEasyAEClientExtension.QuerySourceConditions(client, '', 'OPCLabs.KitEventServer.2',
                                                                     AENodeDescriptor('Simulation.ConditionState1'))
except OpcException as opcException:
    print('*** Failure: ' + opcException.GetBaseException().Message)
    exit()

# Display results.
for conditionElement in conditionElements:
    assert conditionElement is not None
    print('ConditionElements[', conditionElement.Name, ']: ',
          conditionElement.SubconditionNames.Length, ' subcondition(s)',
          sep='')

print()
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

EasyAEClientCore Class
EasyAEClientCore Members

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