OPC Studio User's Guide and Reference
FindGdsRegistrations Method (_EasyUAApplication)
Example 



OpcLabs.EasyOpcUA Assembly > OpcLabs.EasyOpc.UA.Application.ComTypes Namespace > _EasyUAApplication Interface : FindGdsRegistrations Method
The endpoint of OPC UA Global Discovery Server (GDS).

Because the OpcLabs.EasyOpc.UA.UAEndpointDescriptor has implicit conversions from System.String and System.Uri, in languages that support implicit conversion operators (such as C# or VB.NET), you can simply use a string (representing the endpoint URL, or a so-called OPC UA endpoint descriptor string), or a System.Uri object, in place of this parameter, and the corresponding endpoint descriptor will be constructed automatically. When the implicit conversion operators are not supported (such as with Python.NET), you can use the FromString or FromUri static method instead.

Also, because the OpcLabs.EasyOpc.UA.Discovery.UAApplicationElement and OpcLabs.EasyOpc.UA.Discovery.UADiscoveryElement have an implicit conversion to OpcLabs.EasyOpc.UA.UAEndpointDescriptor, in languages that support implicit conversion operators (such as C# or VB.NET), you can simply use a OpcLabs.EasyOpc.UA.Discovery.UAApplicationElement or OpcLabs.EasyOpc.UA.Discovery.UADiscoveryElement (results from OPC UA discovery) in place of this parameter, and the corresponding endpoint descriptor will be constructed automatically. When the implicit conversion operators are not supported (such as with Python.NET), you can convert a (non-null) OpcLabs.EasyOpc.UA.Discovery.UAApplicationElement or OpcLabs.EasyOpc.UA.Discovery.UADiscoveryElement to OpcLabs.EasyOpc.UA.UAEndpointDescriptor using the OpcLabs.EasyOpc.UA.Discovery.UAApplicationElement.ToUAEndpointDescriptor or OpcLabs.EasyOpc.UA.Discovery.UADiscoveryElement.ToUAEndpointDescriptor method instead.

If you are using OPC Wizard (for server development), an implicit conversion from OpcLabs.EasyOpc.UA.EasyUAServerCore can be used in the same way to simply pass the server object in place of this parameter, which will use its OpcLabs.EasyOpc.UA.EasyUAServerCore.EffectiveServerDescriptor property for the connection.

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

Finds all registrations for this application URI in the GDS.
Syntax
'Declaration
 
<NotNullAttribute()>
Function FindGdsRegistrations( _
   ByVal gdsEndpointDescriptor As Object _
) As _UANodeIdUAApplicationElementReadOnlyDictionary
'Usage
 
Dim instance As _EasyUAApplication
Dim gdsEndpointDescriptor As Object
Dim value As _UANodeIdUAApplicationElementReadOnlyDictionary
 
value = instance.FindGdsRegistrations(gdsEndpointDescriptor)

Parameters

gdsEndpointDescriptor
The endpoint of OPC UA Global Discovery Server (GDS).

Because the OpcLabs.EasyOpc.UA.UAEndpointDescriptor has implicit conversions from System.String and System.Uri, in languages that support implicit conversion operators (such as C# or VB.NET), you can simply use a string (representing the endpoint URL, or a so-called OPC UA endpoint descriptor string), or a System.Uri object, in place of this parameter, and the corresponding endpoint descriptor will be constructed automatically. When the implicit conversion operators are not supported (such as with Python.NET), you can use the FromString or FromUri static method instead.

Also, because the OpcLabs.EasyOpc.UA.Discovery.UAApplicationElement and OpcLabs.EasyOpc.UA.Discovery.UADiscoveryElement have an implicit conversion to OpcLabs.EasyOpc.UA.UAEndpointDescriptor, in languages that support implicit conversion operators (such as C# or VB.NET), you can simply use a OpcLabs.EasyOpc.UA.Discovery.UAApplicationElement or OpcLabs.EasyOpc.UA.Discovery.UADiscoveryElement (results from OPC UA discovery) in place of this parameter, and the corresponding endpoint descriptor will be constructed automatically. When the implicit conversion operators are not supported (such as with Python.NET), you can convert a (non-null) OpcLabs.EasyOpc.UA.Discovery.UAApplicationElement or OpcLabs.EasyOpc.UA.Discovery.UADiscoveryElement to OpcLabs.EasyOpc.UA.UAEndpointDescriptor using the OpcLabs.EasyOpc.UA.Discovery.UAApplicationElement.ToUAEndpointDescriptor or OpcLabs.EasyOpc.UA.Discovery.UADiscoveryElement.ToUAEndpointDescriptor method instead.

If you are using OPC Wizard (for server development), an implicit conversion from OpcLabs.EasyOpc.UA.EasyUAServerCore can be used in the same way to simply pass the server object in place of this parameter, which will use its OpcLabs.EasyOpc.UA.EasyUAServerCore.EffectiveServerDescriptor property for the connection.

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

Return Value

Returns a dictionary of OpcLabs.EasyOpc.UA.Discovery.UAApplicationElement objects with application registration information, keyed by a OpcLabs.EasyOpc.UA.AddressSpace.UANodeId which is the application ID identifying the registration in the GDS.

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

The individual elements of the returned value are never null (Nothing in Visual Basic).

Exceptions
ExceptionDescription
An error has occurred during application execution.

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.

The OPC UA 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 identity of the application itself is carried by its application URI, as given by the OpcLabs.EasyOpc.UA.Discovery.UAApplicationElement.ApplicationUriString returned by the OpcLabs.EasyOpc.UA.Application.Extensions.IEasyUAClientServerApplicationExtension.GetApplicationElement. Methods on this interface that manipulate or inspect the GDS registration use the application URI to identify the registration records belonging to this application.

This method queries the Global Discovery Server (GDS) for all registrations associated with this application. It is useful for applications that need to manage their registrations with a GDS, allowing them to discover their own or other applications' registration details.

This method is pure, i.e. it does not have observable side effects.

This member or type is for use from COM. It is not meant to be used from .NET or Python. Refer to the corresponding .NET member or type instead, if you are developing in .NET or Python.

Example
// Shows how to find all application's registrations in the GDS.
// In order to be able to find the registration, run the example for the RegisterToGds method first.
//
// 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.Collections.Generic;
using OpcLabs.EasyOpc.UA;
using OpcLabs.EasyOpc.UA.AddressSpace;
using OpcLabs.EasyOpc.UA.Application;
using OpcLabs.EasyOpc.UA.Application.Extensions;
using OpcLabs.EasyOpc.UA.Discovery;
using OpcLabs.EasyOpc.UA.Extensions;
using OpcLabs.EasyOpc.UA.OperationModel;

namespace UADocExamples.Application._IEasyUAClientServerApplication
{
    class FindGdsRegistrations
    {
        public static void Main1()
        {
            // Define which GDS we will work with.
            UAEndpointDescriptor gdsEndpointDescriptor =
                ((UAEndpointDescriptor)"opc.tcp://opcua.demo-this.com:58810/GlobalDiscoveryServer")
                .WithUserNameIdentity("appadmin", "demo");

            // Obtain the application interface.
            EasyUAApplication application = EasyUAApplication.Instance;

            // Display which application we are about to work with.
            Console.WriteLine("Application URI string: {0}",
                application.GetApplicationElement().ApplicationUriString);

            // Find all application's registrations in the GDS.
            IReadOnlyDictionary<UANodeId, UAApplicationElement> applicationElementDictionary;
            try
            {
                applicationElementDictionary = application.FindGdsRegistrations(gdsEndpointDescriptor);
            }
            catch (UAException uaException)
            {
                Console.WriteLine("*** Failure: {0}", uaException.GetBaseException().Message);
                return;
            }

            // Display results
            foreach (KeyValuePair<UANodeId, UAApplicationElement> pair in applicationElementDictionary)
            {
                Console.WriteLine();
                Console.WriteLine("Application ID: {0}", pair.Key);

                UAApplicationElement applicationElement = pair.Value;
                Console.WriteLine("Application element: {0}", applicationElement);
                Console.WriteLine("  Application URI string: {0}", applicationElement.ApplicationUriString);
                Console.WriteLine("  Discovery URI strings: {0}", applicationElement.DiscoveryUriStrings);
                Console.WriteLine("  Product URI string: {0}", applicationElement.ProductUriString);
            }
        }
    }
}
' Shows how to find all application's registrations in the GDS.
'
' 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.Application
Imports OpcLabs.EasyOpc.UA.Application.Extensions
Imports OpcLabs.EasyOpc.UA.Discovery
Imports OpcLabs.EasyOpc.UA.Extensions
Imports OpcLabs.EasyOpc.UA.OperationModel

Namespace Application._IEasyUAClientServerApplication
    Friend Class FindGdsRegistrations
        Public Shared Sub Main1()

            ' Define which GDS we will work with.
            Dim gdsEndpointDescriptor As UAEndpointDescriptor =
                New UAEndpointDescriptor("opc.tcp://opcua.demo-this.com:58810/GlobalDiscoveryServer") _
                .WithUserNameIdentity("appadmin", "demo")

            ' Obtain the application interface.
            Dim application As EasyUAApplication = EasyUAApplication.Instance

            ' Display which application we are about to work with.
            Console.WriteLine("Application URI string: {0}",
                application.GetApplicationElement().ApplicationUriString)

            ' Find all application's registrations in the GDS.
            Dim applicationElementDictionary As IReadOnlyDictionary(Of UANodeId, UAApplicationElement)
            Try
                applicationElementDictionary = application.FindGdsRegistrations(gdsEndpointDescriptor)
            Catch uaException As UAException
                Console.WriteLine("*** Failure: {0}", uaException.GetBaseException.Message)
                Exit Sub
            End Try

            ' Display results
            For Each pair In applicationElementDictionary
                Console.WriteLine()
                Console.WriteLine("Application ID: {0}", pair.Key)

                Dim applicationElement = pair.Value
                Console.WriteLine("Application element: {0}", applicationElement)
                Console.WriteLine("  Application URI string: {0}", applicationElement.ApplicationUriString)
                Console.WriteLine("  Discovery URI strings: {0}", applicationElement.DiscoveryUriStrings)
                Console.WriteLine("  Product URI string: {0}", applicationElement.ProductUriString)
            Next pair
        End Sub
    End Class
End Namespace
// Shows how to find all application's registrations in the GDS.
//
// 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 FindGdsRegistrations.Main;
var
  Application: TEasyUAApplication;
  ApplicationElement: _UAApplicationElement;
  ApplicationElementDictionary: _UANodeIdUAApplicationElementReadOnlyDictionary;
  ApplicationId: _UANodeId;
  Count: Cardinal;
  Element: OleVariant;
  Enumerator: IEnumVARIANT;
  GdsEndpointDescriptor: _UAEndpointDescriptor;
begin
  // Define which GDS we will work with.
  GdsEndpointDescriptor := CoUAEndpointDescriptor.Create;
  GdsEndpointDescriptor.UrlString := 'opc.tcp://opcua.demo-this.com:58810/GlobalDiscoveryServer';
  GdsEndpointDescriptor.UserIdentity.UserNameTokenInfo.UserName := 'appadmin';
  GdsEndpointDescriptor.UserIdentity.UserNameTokenInfo.Password := 'demo';

  // Obtain the application interface.
  Application := TEasyUAApplication.Create(nil);

  // Display which application we are about to work with.
  WriteLn('Application URI string: ', Application.GetApplicationElement.ApplicationUriString);

  // Find all application's registrations in the GDS.
  try
    ApplicationElementDictionary := Application.FindGdsRegistrations(GdsEndpointDescriptor);
  except
    on E: EOleException do
    begin
      WriteLn(Format('*** Failure: %s', [E.GetBaseException.Message]));
    end;
  end;

  // Display results
  Enumerator := ApplicationElementDictionary.GetEnumerator;
  while (Enumerator.Next(1, Element, Count) = S_OK) do
  begin
    WriteLn;
    ApplicationId := IUnknown(Element.Key) as _UANodeId;
    WriteLn('Application ID: ', ApplicationId.ToString);

    ApplicationElement := IUnknown(Element.Value) as _UAApplicationElement;
    WriteLn('  Application URI string: ', ApplicationElement.ApplicationUriString);
    WriteLn('  Discovery URI string: ', ApplicationElement.DiscoveryUriString);
    WriteLn('  Product URI string: ', ApplicationElement.ProductUriString);
  end;
end;
# Shows how to find all application's registrations in the GDS.
# In order to be able to find the registration, run the example for the RegisterToGds method first.
#
# 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.UA import *
from OpcLabs.EasyOpc.UA.Application import *
from OpcLabs.EasyOpc.UA.Application.Extensions import *
from OpcLabs.EasyOpc.UA.Extensions import *
from OpcLabs.EasyOpc.UA.OperationModel import *


# Define which GDS we will work with.
gdsEndpointDescriptor = UAEndpointDescriptor('opc.tcp://opcua.demo-this.com:58810/GlobalDiscoveryServer')
gdsEndpointDescriptor = UAEndpointDescriptorExtension.WithUserNameIdentity(gdsEndpointDescriptor,
                                                                           'appadmin', 'demo')

# Obtain the application interface.
application = EasyUAApplication.Instance

# Display which application we are about to work with.
applicationElement = IEasyUAClientServerApplicationExtension.GetApplicationElement(application)
print('Application URI string: ', applicationElement.ApplicationUriString, sep='')

# Find all application's registrations in the GDS.
try:
    applicationElementDictionary = application.FindGdsRegistrations(gdsEndpointDescriptor)
except UAException as uaException:
    print('*** Failure: ' + uaException.GetBaseException().Message)
    exit()

# Display results.
for pair in applicationElementDictionary:
    print()
    print('Application ID: ', pair.Key, sep='')

    applicationElement = pair.Value
    print('Application element: ', applicationElement, sep='')
    print('  Application URI string: ', applicationElement.ApplicationUriString, sep='')
    print('  Discovery URI strings: ', applicationElement.DiscoveryUriStrings, sep='')
    print('  Product URI string: ', applicationElement.ProductUriString, 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

See Also