Discover Method (_EasyUAClient)

Discovers available OPC-UA applications or endpoints and returns information about them, using the specified discovery query.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
<NotNullAttribute()>
Function Discover( _
   ByVal discoveryQuery As Object _
) As UADiscoveryElementCollection

'Usage
 
Dim instance As _EasyUAClient
Dim discoveryQuery As Object
Dim value As UADiscoveryElementCollection
 
value = instance.Discover(discoveryQuery)

[NotNull()]
UADiscoveryElementCollection Discover( 
   object discoveryQuery
)

[NotNull()]
UADiscoveryElementCollection^ Discover( 
   Object^ discoveryQuery
)

Parameters

discoveryQuery: Specifies a discovery query.
The value of this parameter cannot be null (Nothing in Visual Basic).

Return Value

Returns a collection of application elements (usually servers, OpcLabs.EasyOpc.UA.Discovery.UADiscoveryElement).

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.UA.OperationModel.UAException	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.

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.UA.OperationModel.UAException

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

This is a generic method that allows for different types of discovery queries. In most cases, it is more practical to use an (extension) method that is already tailored to a concrete type of query, e.g. OpcLabs.EasyOpc.UA.IEasyUAClientExtension.DiscoverLocalApplications, OpcLabs.EasyOpc.UA.IEasyUAClientExtension.DiscoverLocalServers, or OpcLabs.EasyOpc.UA.IEasyUAClientExtension.FindLocalApplications.

See also in Knowledge Base: Technical note-OPC UA Discovery in QuickOPC.

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.

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

_EasyUAClient Interface
_EasyUAClient Members

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