UABrowsePathElement Class

Represents an element in the OPC-UA browse path.

Object Model

Syntax

[CLSCompliant(true)]
[ComDefaultInterface(OpcLabs.EasyOpc.UA.Navigation.ComTypes._UABrowsePathElement)]
[ComVisible(true)]
[Guid("3CE3E988-805D-42AF-AC15-974D93E91240")]
[TypeConverter(OpcLabs.EasyOpc.UA.Navigation.Implementation.UABrowsePathElementConverter)]
[ValueControl("OpcLabs.BaseLib.Forms.Common.ObjectSerializationControl, OpcLabs.BaseLibForms, Version=5.81.455.1, Culture=neutral, PublicKeyToken=6faddca41dacb409", 
   DefaultReadWrite=false, 
   Export=true, 
   PageId=10001)]
[Serializable()]
public sealed class UABrowsePathElement : OpcLabs.BaseLib.Info, LINQPad.ICustomMemberProvider, OpcLabs.BaseLib.ComTypes._Info, OpcLabs.BaseLib.ComTypes._Object2, OpcLabs.EasyOpc.UA.Navigation.ComTypes._UABrowsePathElement, IUABrowsePathElement, System.ICloneable, System.Runtime.Serialization.ISerializable, System.Xml.Serialization.IXmlSerializable

[CLSCompliant(true)]
[ComDefaultInterface(OpcLabs.EasyOpc.UA.Navigation.ComTypes._UABrowsePathElement)]
[ComVisible(true)]
[Guid("3CE3E988-805D-42AF-AC15-974D93E91240")]
[TypeConverter(OpcLabs.EasyOpc.UA.Navigation.Implementation.UABrowsePathElementConverter)]
[ValueControl("OpcLabs.BaseLib.Forms.Common.ObjectSerializationControl, OpcLabs.BaseLibForms, Version=5.81.455.1, Culture=neutral, PublicKeyToken=6faddca41dacb409", 
   DefaultReadWrite=false, 
   Export=true, 
   PageId=10001)]
[Serializable()]
public ref class UABrowsePathElement sealed : public OpcLabs.BaseLib.Info, LINQPad.ICustomMemberProvider, OpcLabs.BaseLib.ComTypes._Info, OpcLabs.BaseLib.ComTypes._Object2, OpcLabs.EasyOpc.UA.Navigation.ComTypes._UABrowsePathElement, IUABrowsePathElement, System.ICloneable, System.Runtime.Serialization.ISerializable, System.Xml.Serialization.IXmlSerializable

'Declaration
 
<CLSCompliantAttribute(True)>
<ComDefaultInterfaceAttribute(OpcLabs.EasyOpc.UA.Navigation.ComTypes._UABrowsePathElement)>
<ComVisibleAttribute(True)>
<GuidAttribute("3CE3E988-805D-42AF-AC15-974D93E91240")>
<TypeConverterAttribute(OpcLabs.EasyOpc.UA.Navigation.Implementation.UABrowsePathElementConverter)>
<ValueControlAttribute("OpcLabs.BaseLib.Forms.Common.ObjectSerializationControl, OpcLabs.BaseLibForms, Version=5.81.455.1, Culture=neutral, PublicKeyToken=6faddca41dacb409", 
   DefaultReadWrite=False, 
   Export=True, 
   PageId=10001)>
<SerializableAttribute()>
Public NotInheritable Class UABrowsePathElement 
   Inherits OpcLabs.BaseLib.Info
   Implements LINQPad.ICustomMemberProvider, OpcLabs.BaseLib.ComTypes._Info, OpcLabs.BaseLib.ComTypes._Object2, OpcLabs.EasyOpc.UA.Navigation.ComTypes._UABrowsePathElement, IUABrowsePathElement, System.ICloneable, System.Runtime.Serialization.ISerializable, System.Xml.Serialization.IXmlSerializable

'Usage
 
Dim instance As UABrowsePathElement

Remarks

There are implicit conversions to this type from:

OpcLabs.EasyOpc.UA.AddressSpace.UAQualifiedName.

OPC UA browse path elements are represented by UABrowsePathElement objects. Each browse path element has following data members:

ReferenceTypeId Property. The type of reference (an instance of UANodeId Class) to follow from the current node. The current path cannot be followed any further if the reference type is not available on the node instance.
ReferenceIsInverse Property. Indicates whether the inverse Reference should be followed.
IncludeSubtypes Property. Indicates whether subtypes of the ReferenceType should be followed.
TargetName Property. The browse name of the target node (an instance of UAQualifiedName Class).

The UABrowsePathElement has various constructor overloads with different combinations of these parameters. In addition, there are static methods on the UABrowsePathElement Class that allow you to easily create commonly used browse path elements:

The Create Method creates a new OPC-UA browse path element with given reference type and target name, for following in forward direction, and including subtypes.
The CreateInverse Method creates a new OPC-UA browse path element with given reference type and target name, for following in inverse direction, and including subtypes.
The CreateSimple Method creates a new OPC-UA browse path element with given target name, and specifying any hierarchical forward reference.
There are static methods for creation of browse path elements for all standard *concrete* references, taking just the target name as input. For example, the HasProperty Method creates a browse path element for following a specific HasProperty reference in a forward direction.

The created browse path elements can then be added to a UABrowsePathElementCollection Class, forming a relative path.

Example

// This example shows how to read a Low state of a limit alarm. Note that you should not normally read a state of an alarm
// from inside its event notification, because the state might have already changed. Instead, include the information you
// need in the Select clauses when subscribing for the event.
//
// 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.UA;
using OpcLabs.EasyOpc.UA.AddressSpace;
using OpcLabs.EasyOpc.UA.Navigation;

namespace UADocExamples.AlarmsAndConditions
{
    class ReadAlarmState
    {
        public static void Main1()
        {
            UAEndpointDescriptor endpointDescriptor =
                "opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer";

            UANodeDescriptor alarmNodeDescriptor = new UANodeId(
                namespaceUriString:"http://opcfoundation.org/Quickstarts/AlarmCondition", 
                identifier:"1:Colours/EastTank?Yellow");

            // Knowing the alarm node, and the fact that is an instance of NonExclusiveLevelAlarmType (or its subtype),
            // determine what is its LowState/Id node.
            UANodeDescriptor lowStateIdNodeDescriptor = new UABrowsePath(alarmNodeDescriptor,
                new []
                {
                    UABrowsePathElement.CreateSimple("ns=0;s=LowState"),
                    UABrowsePathElement.CreateSimple("ns=0;s=Id")
                });

            // Instantiate the client object.
            var client = new EasyUAClient();

            Console.WriteLine("Reading alarm state...");
            var lowStateId = (bool)client.ReadValue(endpointDescriptor, lowStateIdNodeDescriptor);

            Console.WriteLine($"Id of LowState: {lowStateId}");
        }
    }
}

' This example shows how to read a Low state of a limit alarm. Note that you should not normally read a state of an alarm
' from inside its event notification, because the state might have already changed. Instead, include the information you
' need in the Select clauses when subscribing for the event.
'
' 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.UA
Imports OpcLabs.EasyOpc.UA.AddressSpace
Imports OpcLabs.EasyOpc.UA.Navigation

Namespace AlarmsAndConditions
    Friend Class ReadAlarmState
        Public Shared Sub Main1()
            Dim endpointDescriptor As UAEndpointDescriptor =
                "opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer"

            Dim alarmNodeDescriptor As UANodeDescriptor = New UANodeId(
                namespaceUriString:="http://opcfoundation.org/Quickstarts/AlarmCondition",
                identifier:="1:Colours/EastTank?Yellow")

            ' Knowing the alarm node, and the fact that is an instance of NonExclusiveLevelAlarmType (or its subtype),
            ' determine what is its LowState/Id node.
            Dim lowStateIdNodeDescriptor As UANodeDescriptor = New UABrowsePath(alarmNodeDescriptor,
                New UABrowsePathElement() {
                    UABrowsePathElement.CreateSimple("ns=0;s=LowState"),
                    UABrowsePathElement.CreateSimple("ns=0;s=Id")
                })

            ' Instantiate the client object.
            Dim client = New EasyUAClient()

            Console.WriteLine("Reading alarm state...")
            Dim lowStateId = CBool(client.ReadValue(endpointDescriptor, lowStateIdNodeDescriptor))

            Console.WriteLine($"Id of LowState: {lowStateId}")
        End Sub
    End Class
End Namespace

# This example shows how to read a Low state of a limit alarm. Note that you should not normally read a state of an alarm
# from inside its event notification, because the state might have already changed. Instead, include the information you
# need in the Select clauses when subscribing for the event.
#
# 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.EasyOpc.UA import *
from OpcLabs.EasyOpc.UA.AddressSpace.Standard import *
from OpcLabs.EasyOpc.UA.AlarmsAndConditions import *
from OpcLabs.EasyOpc.UA.OperationModel import *


def eventNotification(sender, eventArgs):
    print()
    # Display the event.
    if eventArgs.EventData is None:
        print(eventArgs)
        return
    baseEventObject = eventArgs.EventData.BaseEvent
    print('Source name: ', baseEventObject.SourceName, sep='')
    print('Message: ', baseEventObject.Message, sep='')
    print('Severity: ', baseEventObject.Severity, sep='')


# Define which server we will work with.
endpointDescriptor = UAEndpointDescriptor('opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer')

# Instantiate the client object and hook events.
client = EasyUAClient()
client.EventNotification += eventNotification

print('Subscribing...')
IEasyUAClientExtension.SubscribeEvent(
    client,
    endpointDescriptor,
    UANodeDescriptor(UAObjectIds.Server),
    1000)

print('Processing event notifications for 30 seconds...')
time.sleep(30)

print('Unsubscribing...')
client.UnsubscribeAllMonitoredItems()

print('Waiting for 5 seconds...')
time.sleep(5)

print('Finished.')

Inheritance Hierarchy

System.Object
   OpcLabs.BaseLib.Object2
      OpcLabs.BaseLib.Info
         OpcLabs.EasyOpc.UA.Navigation.UABrowsePathElement

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

UABrowsePathElement Members
OpcLabs.EasyOpc.UA.Navigation Namespace

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