ReadMetricValue Method

Reads from a Sparkplug metric with the specified metric name from the Sparkplug edge node or device and returns the metric value.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
<ExtensionAttribute()>
<JetBrains.Annotations.CanBeNullAttribute()>
Public Shared Function ReadMetricValue( _
   ByVal producer As ISparkplugProducer, _
   ByVal metricName As String _
) As Object

'Usage
 
Dim producer As ISparkplugProducer
Dim metricName As String
Dim value As Object
 
value = ISparkplugProducerExtension.ReadMetricValue(producer, metricName)

[Extension()]
[JetBrains.Annotations.CanBeNull()]
public static object ReadMetricValue( 
   ISparkplugProducer producer,
   string metricName
)

[Extension()]
[JetBrains.Annotations.CanBeNull()]
public:
static Object^ ReadMetricValue( 
   ISparkplugProducer^ producer,
   String^ metricName
)

Parameters

producer: The Sparkplug producer that will perform the operation.
The value of this parameter cannot be null (Nothing in Visual Basic).
metricName: The Sparkplug metric name.
The value of this parameter cannot be null (Nothing in Visual Basic).

Return Value

Returns the value that is the outcome of the read operation.

This method can return 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.
System.InvalidOperationException	A method call was invalid for the object's current state. 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.

System.InvalidOperationException

A method call was invalid for the object's current state.

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

The producer must be started when this method is called, otherwise an System.InvalidOperationException is thrown.

This method throws OpcLabs.EasySparkplug.OperationModel.SparkplugException if the read operation fails.

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.

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

ISparkplugProducerExtension Class
ISparkplugProducerExtension Members

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