WriteValueAction<TValue>(SparkplugMetric,Type,Action<TValue>) Method

Makes a metric that consumes the Sparkplug data using the write value action. Specify the declared type.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
<ExtensionAttribute()>
<JetBrains.Annotations.NotNullAttribute()>
Public Overloads Shared Function WriteValueAction(Of TValue)( _
   ByVal metric As SparkplugMetric, _
   ByVal declaredType As Type, _
   ByVal writeValueAction As Action(Of TValue) _
) As SparkplugMetric

'Usage
 
Dim metric As SparkplugMetric
Dim declaredType As Type
Dim writeValueAction As Action(Of TValue)
Dim value As SparkplugMetric
 
value = SparkplugMetricExtension.WriteValueAction(Of TValue)(metric, declaredType, writeValueAction)

[Extension()]
[JetBrains.Annotations.NotNull()]
public static SparkplugMetric WriteValueAction<TValue>( 
   SparkplugMetric metric,
   Type declaredType,
   Action<TValue> writeValueAction
)

[Extension()]
[JetBrains.Annotations.NotNull()]
public:
static SparkplugMetric^ WriteValueActiongeneric<typename TValue>
( 
   SparkplugMetric^ metric,
   Type^ declaredType,
   Action<TValue^>^ writeValueAction
)

Parameters

metric: The Sparkplug metric that will perform the operation.
The value of this parameter cannot be null (Nothing in Visual Basic).
declaredType: The declared type of the Sparkplug metric, expressed as .NET System.Type.
The value of this parameter cannot be null (Nothing in Visual Basic).
writeValueAction: The write value action, i.e. the action that accepts the value to be written and performs the write operation.
The value of this parameter cannot be null (Nothing in Visual Basic).

Type Parameters

TValue: The type of the value of the Sparkplug metric.

Return Value

Returns the , internally modified as defined by the method.

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.

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.

Remarks

This method always makes the metric writable; however, its timestamp will not be writable, i.e. Sparkplug host applications will not be able to modify them. If you need a different behavior, use one of the WriteFunction(SparkplugMetric,Type,Func<SparkplugData,Boolean>) method overloads instead.

This method does not change the readability access of the metric. By default, metrics are readable. If you need a metric that is writable but non-readable, combine this method with calling Readable(SparkplugMetric,Boolean) method with the 'readable' parameter set to false.

The write operation defined by this method always succeeds. If you need support the option of failing the write operation to fail, use one of the WriteValueFunction<TValue>(SparkplugMetric,Type,Func<TValue,Boolean>) method overloads instead.

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.

Example

CSharp
VB.NET

// This example shows how to define a metric of Sparkplug data type UInt16 and use an action to its write behavior.
// This is an example of the push data consumption model.
//
// You can use any Sparkplug application, including our SparkplugCmd utility and the SparkplugApplicationConsoleDemo
// program, to subscribe to the edge node data. SparkplugCmd, or other capable Sparkplug application, can be used to write
// data into the metric.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-ConnectivityStudio/Latest/examples.html .
// Sparkplug examples in C# on GitHub: https://github.com/OPCLabs/Examples-ConnectivityStudio-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 OpcLabs.EasySparkplug;
using System;

namespace SparkplugDocExamples.EdgeNode._SparkplugMetric
{
    partial class WriteValueAction
    {
        static public void UInt16()
        {
            // Note that the default port for the "mqtt" scheme is 1883.
            var hostDescriptor = new SparkplugHostDescriptor("mqtt://localhost");

            // Instantiate the edge node object and hook events.
            var edgeNode = new EasySparkplugEdgeNode(hostDescriptor, "easyGroup", "easySparkplugDemo");
            edgeNode.SystemConnectionStateChanged += (sender, eventArgs) =>
            {
                // Display the new connection state (such as when the connection to the broker succeeds or fails).
                Console.WriteLine($"{nameof(EasySparkplugEdgeNode.SystemConnectionStateChanged)}: {eventArgs}");
            };

            // Create a writable metric and add an action that will be executed when the metric is written to.
            // We explicitly specify the Sparkplug data type of the variable to be UInt16, but use .NET Int32 in the write value
            // function. EasySparkplug will attempt to convert the value being written to the specified .NET type. This is
            // helpful in languages like VB.NET that do not have full support for some types (such as unsigned integers).
            edgeNode.Add(new SparkplugMetric("WriteToThisMetric").WriteValueAction<int>(
                typeof(UInt16),
                value => Console.WriteLine($"Value written: {value}")));

            // Start the edge node.
            Console.WriteLine("The edge node is starting...");
            edgeNode.Start();

            Console.WriteLine("The edge node is started.");
            Console.WriteLine();

            // Let the user decide when to stop.
            Console.WriteLine("Press Enter to stop the edge node...");
            Console.ReadLine();

            // Stop the edge node.
            Console.WriteLine("The edge node is stopping...");
            edgeNode.Stop();

            Console.WriteLine("The edge node is stopped.");
        }
    }
}

' This example shows how to define a metric of Sparkplug data type UInt16 and use an action to its write behavior.
' This is an example of the push data consumption model.
'
' You can use any Sparkplug application, including our SparkplugCmd utility and the SparkplugApplicationConsoleDemo
' program, to subscribe to the edge node data. SparkplugCmd, or other capable Sparkplug application, can be used to write
' data into the metric.
'
' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-ConnectivityStudio/Latest/examples.html .
' Sparkplug examples in C# on GitHub: https://github.com/OPCLabs/Examples-ConnectivityStudio-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.

Imports OpcLabs.EasySparkplug

Namespace Global.SparkplugDocExamples.EdgeNode._SparkplugMetric
    Partial Class WriteValueAction
        Public Shared Sub UInt16()
            ' Note that the default port for the "mqtt" scheme is 1883.
            Dim hostDescriptor = New SparkplugHostDescriptor("mqtt://localhost")

            ' Instantiate the edge node object and hook events.
            Dim edgeNode = New EasySparkplugEdgeNode(hostDescriptor, "easyGroup", "easySparkplugDemo")
            AddHandler edgeNode.SystemConnectionStateChanged,
                Sub(sender, eventArgs)
                    ' Display the new connection state (such as when the connection to the broker succeeds or fails).
                    Console.WriteLine($"{NameOf(EasySparkplugEdgeNode.SystemConnectionStateChanged)}: {eventArgs}")
                End Sub

            ' Create a writable metric and add an action that will be executed when the metric is written to.
            ' We explicitly specify the Sparkplug data type of the variable to be UInt16, but use .NET Int32 in the write value
            ' function. EasySparkplug will attempt to convert the value being written to the specified .NET type. This is
            ' helpful in languages like VB.NET that do not have full support for some types (such as unsigned integers).
            edgeNode.Add(New SparkplugMetric("WriteToThisMetric").WriteValueAction(Of Integer)(
                GetType(UInt16),
                Sub(value) Console.WriteLine($"Value written: {value}")))

            ' Start the edge node.
            Console.WriteLine("The edge node is starting...")
            edgeNode.Start()

            Console.WriteLine("The edge node is started.")
            Console.WriteLine()

            ' Let the user decide when to stop.
            Console.WriteLine("Press Enter to stop the edge node...")
            Console.ReadLine()

            ' Stop the edge node.
            Console.WriteLine("The edge node is stopping...")
            edgeNode.Stop()

            Console.WriteLine("The edge node is stopped.")
        End Sub
    End Class
End Namespace

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

SparkplugMetricExtension Class
SparkplugMetricExtension Members
Overload List

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