BrowseLeaves(IEasyDAClient,ServerDescriptor,DANodeDescriptor,String) Method

Browse for child leaves. Specify server descriptor, and element name filter.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
<ExtensionAttribute()>
<NotNullAttribute()>
Public Overloads Shared Function BrowseLeaves( _
   ByVal client As IEasyDAClient, _
   ByVal serverDescriptor As ServerDescriptor, _
   ByVal parentNodeDescriptor As DANodeDescriptor, _
   ByVal elementNameFilter As String _
) As DANodeElementCollection

'Usage
 
Dim client As IEasyDAClient
Dim serverDescriptor As ServerDescriptor
Dim parentNodeDescriptor As DANodeDescriptor
Dim elementNameFilter As String
Dim value As DANodeElementCollection
 
value = IEasyDAClientExtension.BrowseLeaves(client, serverDescriptor, parentNodeDescriptor, elementNameFilter)

[Extension()]
[NotNull()]
public static DANodeElementCollection BrowseLeaves( 
   IEasyDAClient client,
   ServerDescriptor serverDescriptor,
   DANodeDescriptor parentNodeDescriptor,
   string elementNameFilter
)

[Extension()]
[NotNull()]
public:
static DANodeElementCollection^ BrowseLeaves( 
   IEasyDAClient^ client,
   ServerDescriptor^ serverDescriptor,
   DANodeDescriptor^ parentNodeDescriptor,
   String^ elementNameFilter
)

Parameters

client

The client object that will perform the operation.

This is typically the EasyDAClient object.

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

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 FromGuid, FromString or FromServerElement static method instead.

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

parentNodeDescriptor

Descriptor for the parent branch to be browsed (can be the root).

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

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

elementNameFilter

A wildcard string to filter the returned element names (empty string for no filtering)

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

Return Value

The method returns a keyed collection of OpcLabs.EasyOpc.DataAccess.AddressSpace.DANodeElement values, each containing information about a particular leaf found. The keys of the keyed collection are the names of the leaves.

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.

Remarks

This is an extension method (info: C#, VB.NET). In languages that have support for extensions methods (such as C# and VB.NET), you can use the extension method as if it were a regular method on the object that is its first parameter. In other languages (such as with Python.NET), you will call the extension as a static method, and pass it the object on which it acts as its first parameter.

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

IEasyDAClientExtension Class
IEasyDAClientExtension Members
Overload List

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