OPC Studio User's Guide and Reference
DAWriteItemValueObserver<TValue> Class
Members  Example 



OpcLabs.EasyOpcClassic Assembly > OpcLabs.EasyOpc.DataAccess.Reactive Namespace : DAWriteItemValueObserver<TValue> Class
The type of OPC values received.
Push-based notification receiver (observer) that writes incoming values into an OPC Data Access item.
Object Model
DAWriteItemValueObserver<TValue> ClassEasyDAClientSelector ClassDAItemArguments Class
Syntax
'Declaration
 
<ComVisibleAttribute(False)>
<TypeConverterAttribute(System.ComponentModel.ExpandableObjectConverter)>
<CLSCompliantAttribute(True)>
<ValueControlAttribute("OpcLabs.BaseLib.Forms.Common.ObjectSerializationControl, OpcLabs.BaseLibForms, Version=5.80.82.1, Culture=neutral, PublicKeyToken=6faddca41dacb409", 
   DefaultReadWrite=False, 
   Export=True, 
   PageId=10001)>
<SerializableAttribute()>
Public NotInheritable Class DAWriteItemValueObserver(Of TValue) 
   Inherits DAReactive
   Implements LINQPad.ICustomMemberProvider, OpcLabs.BaseLib.ComTypes._Info, OpcLabs.BaseLib.ComTypes._Object2, System.ICloneable, System.IObserver(Of TValue), System.Runtime.Serialization.ISerializable, System.Xml.Serialization.IXmlSerializable 
'Usage
 
Dim instance As DAWriteItemValueObserver(Of TValue)
[ComVisible(false)]
[TypeConverter(System.ComponentModel.ExpandableObjectConverter)]
[CLSCompliant(true)]
[ValueControl("OpcLabs.BaseLib.Forms.Common.ObjectSerializationControl, OpcLabs.BaseLibForms, Version=5.80.82.1, Culture=neutral, PublicKeyToken=6faddca41dacb409", 
   DefaultReadWrite=false, 
   Export=true, 
   PageId=10001)]
[Serializable()]
public sealed class DAWriteItemValueObserver<TValue> : DAReactive, LINQPad.ICustomMemberProvider, OpcLabs.BaseLib.ComTypes._Info, OpcLabs.BaseLib.ComTypes._Object2, System.ICloneable, System.IObserver<TValue>, System.Runtime.Serialization.ISerializable, System.Xml.Serialization.IXmlSerializable  
[ComVisible(false)]
[TypeConverter(System.ComponentModel.ExpandableObjectConverter)]
[CLSCompliant(true)]
[ValueControl("OpcLabs.BaseLib.Forms.Common.ObjectSerializationControl, OpcLabs.BaseLibForms, Version=5.80.82.1, Culture=neutral, PublicKeyToken=6faddca41dacb409", 
   DefaultReadWrite=false, 
   Export=true, 
   PageId=10001)]
[Serializable()]
generic<typename TValue>
public ref class DAWriteItemValueObserver sealed : public DAReactive, LINQPad.ICustomMemberProvider, OpcLabs.BaseLib.ComTypes._Info, OpcLabs.BaseLib.ComTypes._Object2, System.ICloneable, System.IObserver<TValue>, System.Runtime.Serialization.ISerializable, System.Xml.Serialization.IXmlSerializable  
Type Parameters
TValue
The type of OPC values received.
Example

.NET

.NET

// Shows how to create an observer that writes values to OPC-DA item, and subscribe it to a generated sequence of values.
// Requires Microsoft Reactive Extensions (Rx).
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

using System;
using System.Reactive.Linq;
using System.Threading;
using OpcLabs.EasyOpc.DataAccess;
using OpcLabs.EasyOpc.DataAccess.Reactive;

namespace ReactiveDocExamples
{
    namespace _DAWriteItemValueObserver
    {
        class OnNext
        {
            public static void Main1()
            {
                Console.WriteLine("Creating source observable, 0..9 in 1 second intervals...");
                IObservable<int> source = Observable.Generate(0, i => i < 10, i => i + 1, i => i, i => TimeSpan.FromSeconds(1));

                Console.WriteLine("Creating observer to write values into OPC item...");
                DAWriteItemValueObserver<int> observer =
                    DAWriteItemValueObserver.Create<int>("", "OPCLabs.KitServer.2", "Simulation.Register_I4");

                Console.WriteLine("Monitoring changes of the target OPC item using traditional means...");
                int handle = EasyDAClient.SharedInstance.SubscribeItem("", "OPCLabs.KitServer.2", "Simulation.Register_I4", 
                    100, (_, e) => Console.WriteLine(e.Vtq));

                Console.WriteLine("Subscribing the observer to source observable...");
                source.Subscribe(observer);

                Console.WriteLine("Waiting for 10 seconds...");
                Thread.Sleep(10 * 1000);

                Console.WriteLine("Finalizing monitoring...");
                EasyDAClient.SharedInstance.UnsubscribeItem(handle);

                Console.WriteLine("Waiting for 2 seconds...");
                Thread.Sleep(2 * 1000);
            }
        }
    }
}
// Shows how to continuously transform values of OPC-DA item, and write the results into a second item.
// Requires Microsoft Reactive Extensions (Rx).
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

using System;
using System.Reactive.Linq;
using System.Threading;
using OpcLabs.EasyOpc.DataAccess;
using OpcLabs.EasyOpc.DataAccess.Reactive;

namespace ReactiveDocExamples
{
    namespace _DAReactive
    {
        class Composition
        {
            public static void Pipeline()
            {
                Console.WriteLine("Creating source observable...");
                DAItemChangedObservable<int> source =
                    DAItemChangedObservable.Create<int>("", "OPCLabs.KitServer.2", "Simulation.Incrementing (1 s)", 100);

                Console.WriteLine("Creating processed observable (takes valid input values and multiplies them by 1000)...");
                IObservable<int> processed = source
                    .Where(e => e.Exception is null)
                    .Select(e => e.TypedVtq.TypedValue * 1000);

                Console.WriteLine("Creating observer to write values into OPC item...");
                DAWriteItemValueObserver<int> observer = 
                    DAWriteItemValueObserver.Create<int>("", "OPCLabs.KitServer.2", "Simulation.Register_I4");

                Console.WriteLine("Monitoring changes of the target OPC item using traditional means...");
                int handle = EasyDAClient.SharedInstance.SubscribeItem("", "OPCLabs.KitServer.2", "Simulation.Register_I4",
                    100, (_, e) => Console.WriteLine(e.Vtq));

                Console.WriteLine("Subscribing the observer to the processed observable...");
                using (processed.Subscribe(observer))
                {
                    Console.WriteLine("Waiting for 10 seconds...");
                    Thread.Sleep(10 * 1000);

                    Console.WriteLine("Unsubscribing the observer from the processed observable...");
                }

                Console.WriteLine("Finalizing monitoring...");
                EasyDAClient.SharedInstance.UnsubscribeItem(handle);

                Console.WriteLine("Waiting for 2 seconds...");
                Thread.Sleep(2 * 1000);
            }
        }
    }
}
Inheritance Hierarchy

System.Object
   OpcLabs.BaseLib.Object2
      OpcLabs.BaseLib.Info
         OpcLabs.EasyOpc.DataAccess.Reactive.DAReactive
            OpcLabs.EasyOpc.DataAccess.Reactive.DAWriteItemValueObserver<TValue>

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