FindOrCreateHostApplication Method (EasySparkplugSystem)

Find an existing Sparkplug host application by its host ID, or create a new one (and add it to the system) if it does not exist.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
<JetBrains.Annotations.NotNullAttribute()>
Public Function FindOrCreateHostApplication( _
   ByVal hostId As String _
) As EasySparkplugHostApplication

'Usage
 
Dim instance As EasySparkplugSystem
Dim hostId As String
Dim value As EasySparkplugHostApplication
 
value = instance.FindOrCreateHostApplication(hostId)

[JetBrains.Annotations.NotNull()]
public EasySparkplugHostApplication FindOrCreateHostApplication( 
   string hostId
)

[JetBrains.Annotations.NotNull()]
public:
EasySparkplugHostApplication^ FindOrCreateHostApplication( 
   String^ hostId
)

Parameters

hostId

The Sparkplug host ID.

The value represents a Sparkplug host ID. It must be a string with valid UTF-8 characters except for the reserved characters of '+' (plus) and '#' (number sign).

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

Return Value

Returns the Sparkplug host application that has been found or created.

This method never returns 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.EasySparkplug.OperationModel.SparkplugException	The Sparkplug 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.EasySparkplug.OperationModel.SparkplugException

The Sparkplug 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

If the hostId is an empty string, the method will use the AutoGeneratedHostId instead.

This method attempts to find an existing host application by its host ID first, and returns it if it was found. Otherwise, it creates a new one with the specified hostId.

A new Sparkplug host application is only ever created by this method if AutoCreateHostApplication is true (which is the default). If a host application is not found and AutoCreateHostApplication is false, this method throws a OpcLabs.EasySparkplug.OperationModel.SparkplugException.

Sparkplug is a trademark of Eclipse Foundation, Inc. "MQTT" is a trademark of the OASIS Open standards consortium. Other related terms are trademarks of their respective owners. Any use of these terms on this site is for descriptive purposes only and does not imply any sponsorship, endorsement or affiliation.

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

EasySparkplugSystem Class
EasySparkplugSystem Members

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