OPC Studio User's Guide and Reference
SubscribeDataSet(IEasyUASubscriber,UASubscribeDataSetArguments,EasyUADataSetMessageEventHandler) Method
Example 



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OpcLabs.EasyOpcUA Assembly > OpcLabs.EasyOpc.UA.PubSub Namespace > IEasyUASubscriberExtension Class > SubscribeDataSet Method : SubscribeDataSet(IEasyUASubscriber,UASubscribeDataSetArguments,EasyUADataSetMessageEventHandler) Method
The subscriber object that will perform the operation.

This is typically the EasyUASubscriber object.

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

Holds all arguments needed to subscribe to a dataset in OPC UA PubSub.

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

A callback method to be invoked for each dataset message received.

The value of this parameter can be null (Nothing in Visual Basic).

Subscribes to a dataset, using arguments object, and an optional callback.
Syntax
'Declaration
 

<ExtensionAttribute()>
Public Overloads Shared Function SubscribeDataSet( _
   ByVal subscriber As IEasyUASubscriber, _
   ByVal subscribeDataSetArguments As UASubscribeDataSetArguments, _
   ByVal callback As EasyUADataSetMessageEventHandler _
) As Integer
 
'Usage
 

Dim subscriber As IEasyUASubscriber
Dim subscribeDataSetArguments As UASubscribeDataSetArguments
Dim callback As EasyUADataSetMessageEventHandler
Dim value As Integer
 
value = IEasyUASubscriberExtension.SubscribeDataSet(subscriber, subscribeDataSetArguments, callback)

Parameters

subscriber
The subscriber object that will perform the operation.

This is typically the EasyUASubscriber object.

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

subscribeDataSetArguments
Holds all arguments needed to subscribe to a dataset in OPC UA PubSub.

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

callback
A callback method to be invoked for each dataset message received.

The value of this parameter can be null (Nothing in Visual Basic).

Return Value

Returns a dataset subscription handle that can be used to change the subscription, obtain its arguments, or unsubscribe.
Exceptions
ExceptionDescription
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 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.

 

This method operates (at least in part) asynchronously, with respect to the caller. The actual execution of the operation may be delayed, and the outcome of the operation (if any) is provided to the calling code using an event notification, callback, or other means explained in the text. In a properly written program, this method does not throw any exceptions. You should therefore not put try/catch statements or similar constructs around calls to this method. The only exceptions thrown by this method are for usage errors, i.e. when your code violates the usage contract of the method, such as passing in invalid arguments or calling the method when the state of the object does not allow it. Any operation-related errors (i.e. errors that depend on external conditions that your code cannot reliably check) are indicated by the means the operation returns its outcome (if any), which is described in the text. For more information, see Do not catch any exceptions with asynchronous or multiple-operation methods.
Example
// This example shows how to subscribe to all dataset messages on an OPC-UA PubSub connection, and process them using
// a callback method.
//
// In order to produce network messages for this example, run the UADemoPublisher tool. For documentation, see
// https://kb.opclabs.com/UADemoPublisher_Basics . In some cases, you may have to specify the interface name to be used.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// OPC client and subscriber examples in C# on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-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 System;
using System.Collections.Generic;
using System.Threading;
using OpcLabs.EasyOpc.UA.PubSub;

namespace UASubscriberDocExamples.PubSub._EasyUASubscriber
{
    partial class SubscribeDataSet
    {
        public static void Callback()
        {
            // Define the PubSub connection we will work with. Uses implicit conversion from a string.
            UAPubSubConnectionDescriptor pubSubConnectionDescriptor = "opc.udp://239.0.0.1";
            // In some cases you may have to set the interface (network adapter) name that needs to be used, similarly to
            // the statement below. Your actual interface name may differ, of course.
            //pubSubConnectionDescriptor.ResourceAddress.InterfaceName = "Ethernet";

            // Instantiate the subscriber object.
            var subscriber = new EasyUASubscriber();

            Console.WriteLine("Subscribing...");
            subscriber.SubscribeDataSet(pubSubConnectionDescriptor, (sender, args) => 
            {
                // Display the dataset.
                if (args.Succeeded)
                {
                    // An event with null DataSetData just indicates a successful connection.
                    if (!(args.DataSetData is null))
                    {
                        Console.WriteLine();
                        Console.WriteLine($"Dataset data: {args.DataSetData}");
                        foreach (KeyValuePair<string, UADataSetFieldData> pair in args.DataSetData.FieldDataDictionary)
                            Console.WriteLine(pair);
                    }
                }
                else
                {
                    Console.WriteLine();
                    Console.WriteLine($"*** Failure: {args.ErrorMessageBrief}");
                }
            });

            Console.WriteLine("Processing dataset message events for 20 seconds...");
            Thread.Sleep(20 * 1000);

            Console.WriteLine("Unsubscribing...");
            subscriber.UnsubscribeAllDataSets();

            Console.WriteLine("Waiting for 1 second...");
            // Unsubscribe operation is asynchronous, messages may still come for a short while.
            Thread.Sleep(1 * 1000);

            Console.WriteLine("Finished.");
        }

        // Example output:
        //
        //Subscribing...
        //Processing dataset message events for 20 seconds...
        //
        //Dataset data: Good; Data; publisher="32", writer=1, class=eae79794-1af7-4f96-8401-4096cd1d8908, fields: 4
        //[#0, True {System.Boolean} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
        //[#1, 7945 {System.Int32} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
        //[#2, 5246 {System.Int32} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
        //[#3, 9/30/2019 11:19:14 AM {System.DateTime} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
        //
        //Dataset data: Good; Data; publisher="32", writer=3, class=96976b7b-0db7-46c3-a715-0979884b55ae, fields: 100
        //[#0, 45 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
        //[#1, 145 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
        //[#2, 245 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
        //[#3, 345 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
        //[#4, 445 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
        //[#5, 545 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
        //[#6, 645 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
        //[#7, 745 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
        //[#8, 845 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
        //[#9, 945 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
        //[#10, 1045 {System.Int64} @0001-01-01T00:00:00.000 @@0001-01-01T00:00:00.000; Good]
        //...
    }
}
Requirements

Target Platforms: .NET Framework: Windows 10 (selected versions), Windows 11 (selected versions), Windows Server 2016, Windows Server 2022; .NET: Linux, macOS, Microsoft Windows

See Also

Reference

IEasyUASubscriberExtension Class
IEasyUASubscriberExtension Members
Overload List

 

 

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