Push-based notification provider (observable) for changes in OPC Data Access item(s).
Object Model
Syntax
[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 DAItemChangedObservable<> : DAReactive, LINQPad.ICustomMemberProvider, OpcLabs.BaseLib.ComTypes._Info, OpcLabs.BaseLib.ComTypes._Object2, System.ICloneable, System.IObservable<EasyDAItemChangedEventArgs<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 >
public ref class DAItemChangedObservable sealed : public DAReactive, LINQPad.ICustomMemberProvider, OpcLabs.BaseLib.ComTypes._Info, OpcLabs.BaseLib.ComTypes._Object2, System.ICloneable, System.IObservable<EasyDAItemChangedEventArgs<TValue>>, System.Runtime.Serialization.ISerializable, System.Xml.Serialization.IXmlSerializable
'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 DAItemChangedObservable(Of )
Inherits DAReactive
Implements LINQPad.ICustomMemberProvider, OpcLabs.BaseLib.ComTypes._Info, OpcLabs.BaseLib.ComTypes._Object2, System.ICloneable, System.IObservable(Of EasyDAItemChangedEventArgs(Of TValue)), System.Runtime.Serialization.ISerializable, System.Xml.Serialization.IXmlSerializable
Type Parameters
- TValue
- The type of OPC values provided.
Example
.NET
.NET
.NET
// Shows how to create an observable for OPC-DA item changes, and subscribe to it.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
using System;
using System.Threading;
using OpcLabs.EasyOpc.DataAccess.Reactive;
namespace ReactiveDocExamples
{
namespace _DAItemChangedObservable
{
partial class Subscribe
{
public static void Main1()
{
Console.WriteLine("Creating observable...");
DAItemChangedObservable<double> ramp =
DAItemChangedObservable.Create<double>("", "OPCLabs.KitServer.2", "Demo.Ramp", 1000);
Console.WriteLine("Subscribing...");
using (ramp.Subscribe(e => Console.WriteLine(
(e.Exception is null) ? e.Vtq.ToString() : e.Exception.GetBaseException().ToString())))
{
Console.WriteLine("Waiting for 10 seconds...");
Thread.Sleep(10*1000);
Console.WriteLine("Unsubscribing...");
}
Console.WriteLine("Waiting for 2 seconds...");
Thread.Sleep(2 * 1000);
}
}
}
}
// Shows how to create an observable for OPC-DA item changes, and subscribe to it with percent deadband.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
using System;
using System.Threading;
using OpcLabs.EasyOpc.DataAccess.Reactive;
namespace ReactiveDocExamples
{
namespace _DAItemChangedObservable
{
partial class Subscribe
{
public static void PercentDeadband()
{
const float percentDeadband = 5.0f;
Console.WriteLine($"Creating observable with {percentDeadband}% deadband...");
DAItemChangedObservable<double> ramp =
DAItemChangedObservable.Create<double>("", "OPCLabs.KitServer.2", "Simulation.Ramp 0:100 (10 s)",
requestedUpdateRate:100, percentDeadband:percentDeadband);
Console.WriteLine("Subscribing...");
using (ramp.Subscribe(e => Console.WriteLine(
(e.Exception is null) ? e.Vtq.ToString() : e.Exception.GetBaseException().ToString())))
{
Console.WriteLine("Waiting for 10 seconds...");
Thread.Sleep(10*1000);
Console.WriteLine("Unsubscribing...");
}
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
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