'Declaration
Event ItemChanged As EasyDAItemChangedEventHandler
'Usage
Dim instance As IEasyDAClient Dim handler As EasyDAItemChangedEventHandler AddHandler instance.ItemChanged, handler
event EasyDAItemChangedEventHandler ItemChanged
event EasyDAItemChangedEventHandler^ ItemChanged
Event Data
The event handler receives an argument of type EasyDAItemChangedEventArgs containing data related to this event. The following EasyDAItemChangedEventArgs properties provide information specific to this event.
Property | Description |
---|---|
Arguments | Holds arguments that were used to subscribe to an item in an OPC-DA server. |
Diagnostics | Diagnostics information (such as warnings) assembled during the operation. (Inherited from OpcLabs.BaseLib.OperationModel.OperationEventArgs) |
DiagnosticsCount | Count of diagnostic information elements assembled during the operation. (Inherited from OpcLabs.BaseLib.OperationModel.OperationEventArgs) |
DiagnosticsSummary | Textual summary of diagnostics information, one message per line. (Inherited from OpcLabs.BaseLib.OperationModel.OperationEventArgs) |
ErrorId | Gets or sets the error ID of the error. (Inherited from OpcLabs.BaseLib.OperationModel.OperationEventArgs) |
ErrorMessage | Gets or sets a message that describes the current exception. (Inherited from OpcLabs.BaseLib.OperationModel.OperationEventArgs) |
ErrorMessageBrief | The first line of the error message. (Inherited from OpcLabs.BaseLib.OperationModel.OperationEventArgs) |
Exception | Gets the current exception. Contains null reference when no exception. (Inherited from OpcLabs.BaseLib.OperationModel.OperationEventArgs) |
NormalizedDiagnostics | A normalized OpcLabs.BaseLib.OperationModel.OperationEventArgs.Diagnostics collection. (Inherited from OpcLabs.BaseLib.OperationModel.OperationEventArgs) |
NormalizedException | A normalized OpcLabs.BaseLib.OperationModel.OperationEventArgs.Exception object, or null if there was no error. (Inherited from OpcLabs.BaseLib.OperationModel.OperationEventArgs) |
StatusInfo | Status information corresponding to the contents of the event arguments. |
Succeeded | Gets indication whether the operation has succeeded. (Inherited from OpcLabs.BaseLib.OperationModel.OperationEventArgs) |
Vtq | Gets the current (new) OpcLabs.EasyOpc.DataAccess.DAVtq (value, timestamp and quality) of the OPC item. Null reference when System.Exception is not null. |
Example
.NET
.NET
.NET
// This example shows how subscribe to changes of multiple items and display each change, identifying the different // subscriptions by an integer. // // 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; using OpcLabs.EasyOpc.DataAccess.OperationModel; namespace DocExamples.DataAccess._EasyDAClient { partial class SubscribeMultipleItems { public static void StateAsInteger() { // Instantiate the client object. using (var client = new EasyDAClient()) { // Hook events client.ItemChanged += client_StateAsInteger_ItemChanged; Console.WriteLine("Subscribing..."); int[] handleArray = client.SubscribeMultipleItems(new[] { new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Random", 1000, state: 1), // An integer we have chosen to identify the subscription new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Trends.Ramp (1 min)", 1000, state: 2), // An integer we have chosen to identify the subscription new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Trends.Sine (1 min)", 1000, state: 3), // An integer we have chosen to identify the subscription new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Register_I4", 1000, state: 4) // An integer we have chosen to identify the subscription }); for (int i = 0; i < handleArray.Length; i++) Console.WriteLine($"handleArray[{i}]: {handleArray[i]}"); Console.WriteLine("Processing item changed events for 10 seconds..."); Thread.Sleep(10 * 1000); Console.WriteLine("Unsubscribing..."); } Console.WriteLine("Waiting for 5 seconds..."); Thread.Sleep(5 * 1000); Console.WriteLine("Finished."); } // Item changed event handler static void client_StateAsInteger_ItemChanged(object sender, EasyDAItemChangedEventArgs eventArgs) { // Obtain the integer state we have passed in. var stateAsInteger = (int)eventArgs.Arguments.State; // Display the data if (eventArgs.Succeeded) Console.WriteLine($"{stateAsInteger}: {eventArgs.Vtq}"); else Console.WriteLine($"{stateAsInteger} *** Failure: {eventArgs.ErrorMessageBrief}"); } } }
# This example shows how subscribe to changes of multiple items and display each change, identifying the different # subscriptions by an integer. # # Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . # OPC client and subscriber examples in Python on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-Python . # The QuickOPC package is needed. Install it using "pip install opclabs_quickopc". import opclabs_quickopc import time # Import .NET namespaces. from OpcLabs.EasyOpc.DataAccess import * from OpcLabs.EasyOpc.DataAccess.OperationModel import * # Item changed event handler. def itemChanged(sender, eventArgs): # Obtain the integer state we have passed in. stateAsInteger = int(eventArgs.Arguments.State) if eventArgs.Succeeded: print(stateAsInteger, ': ', eventArgs.Vtq, sep='') else: print(stateAsInteger, ' *** Failure: ', eventArgs.ErrorMessageBrief, sep='') # Instantiate the client object. client = EasyDAClient() # Hook events. client.ItemChanged += itemChanged print('Subscribing item changes...') handleArray = IEasyDAClientExtension.SubscribeMultipleItems(client, [ DAItemGroupArguments('', 'OPCLabs.KitServer.2', 'Simulation.Random', 1000, 1), # an integer we have chosen to identify the subscription DAItemGroupArguments('', 'OPCLabs.KitServer.2', 'Trends.Ramp (1 min)', 1000, 2), # an integer we have chosen to identify the subscription DAItemGroupArguments('', 'OPCLabs.KitServer.2', 'Trends.Sine (1 min)', 1000, 3), # an integer we have chosen to identify the subscription DAItemGroupArguments('', 'OPCLabs.KitServer.2', 'Simulation.Register_I4', 1000, 4), # an integer we have chosen to identify the subscription ]) for i in range(len(handleArray)): print('handleArray[', i, ']: ', handleArray[i], sep='') print('Processing item change notifications for 1 minute...') time.sleep(60) print('Unsubscribing all items...') client.UnsubscribeAllItems() client.ItemChanged -= itemChanged print('Finished.')
' This example shows how subscribe to changes of multiple items and display each change, identifying the different ' subscriptions by an integer. ' ' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . Imports System.Threading Imports OpcLabs.EasyOpc.DataAccess Imports OpcLabs.EasyOpc.DataAccess.OperationModel Namespace DataAccess._EasyDAClient Partial Friend Class SubscribeMultipleItems Public Shared Sub StateAsInteger() ' Instantiate the client object. Using client = New EasyDAClient() AddHandler client.ItemChanged, AddressOf client_StateAsInteger_ItemChanged Console.WriteLine("Subscribing...") Dim handleArray() As Integer = client.SubscribeMultipleItems(New DAItemGroupArguments() { New DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Random", 1000, state:=1), ' An integer we have chosen to identify the subscription New DAItemGroupArguments("", "OPCLabs.KitServer.2", "Trends.Ramp (1 min)", 1000, state:=2), ' An integer we have chosen to identify the subscription New DAItemGroupArguments("", "OPCLabs.KitServer.2", "Trends.Sine (1 min)", 1000, state:=3), ' An integer we have chosen to identify the subscription New DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Register_I4", 1000, state:=4) ' An integer we have chosen to identify the subscription }) For i As Integer = 0 To handleArray.Length - 1 Console.WriteLine($"handleArray[{i}]: {handleArray(i)}") Next i Console.WriteLine("Processing item changed events for 10 seconds...") Thread.Sleep(10 * 1000) Console.WriteLine("Unsubscribing...") End Using Console.WriteLine("Waiting for 5 seconds...") Thread.Sleep(5 * 1000) Console.WriteLine("Finished.") End Sub ' Item changed event handler Private Shared Sub client_StateAsInteger_ItemChanged(ByVal sender As Object, ByVal eventArgs As EasyDAItemChangedEventArgs) ' Obtain the integer state we have passed in. Dim stateAsInteger As Integer = CInt(eventArgs.Arguments.State) If eventArgs.Succeeded Then Console.WriteLine($"{stateAsInteger}: {eventArgs.Vtq}") Else Console.WriteLine($"{stateAsInteger} *** Failure: {eventArgs.ErrorMessageBrief}") End If End Sub End Class End Namespace
// This example shows how subscribe to changes of multiple items and display each change, identifying the different // subscriptions by an object. // // 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; using OpcLabs.EasyOpc.DataAccess.OperationModel; namespace DocExamples.DataAccess._EasyDAClient { partial class SubscribeMultipleItems { class CustomObject { public CustomObject(string name) { Name = name; } public string Name { get; } } public static void StateAsObject() { // Instantiate the client object. using (var client = new EasyDAClient()) { // Hook events client.ItemChanged += client_StateAsObject_ItemChanged; Console.WriteLine("Subscribing..."); int[] handleArray = client.SubscribeMultipleItems(new[] { new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Random", 1000, new CustomObject("First")), // A custom object that corresponds to the subscription new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Trends.Ramp (1 min)", 1000, new CustomObject("Second")), // A custom object that corresponds to the subscription new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Trends.Sine (1 min)", 1000, new CustomObject("Third")), // A custom object that corresponds to the subscription new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Register_I4", 1000, new CustomObject("Fourth")) // A custom object that corresponds to the subscription }); for (int i = 0; i < handleArray.Length; i++) Console.WriteLine($"handleArray[{i}]: {handleArray[i]}"); Console.WriteLine("Processing item changed events for 10 seconds..."); Thread.Sleep(10 * 1000); Console.WriteLine("Unsubscribing..."); } Console.WriteLine("Waiting for 5 seconds..."); Thread.Sleep(5 * 1000); Console.WriteLine("Finished."); } // Item changed event handler static void client_StateAsObject_ItemChanged(object sender, EasyDAItemChangedEventArgs eventArgs) { // Obtain the custom object we have passed in. var stateAsObject = (CustomObject)eventArgs.Arguments.State; // Display the data if (eventArgs.Succeeded) Console.WriteLine($"{stateAsObject.Name}: {eventArgs.Vtq}"); else Console.WriteLine($"{stateAsObject.Name} *** Failure: {eventArgs.ErrorMessageBrief}"); } } }
# This example shows how subscribe to changes of multiple items and display each change, identifying the different # subscriptions by an object. # # Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . # OPC client and subscriber examples in Python on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-Python . # The QuickOPC package is needed. Install it using "pip install opclabs_quickopc". import opclabs_quickopc import time # Import .NET namespaces. from OpcLabs.EasyOpc.DataAccess import * from OpcLabs.EasyOpc.DataAccess.OperationModel import * class CustomObject(object): def __init__(self, name): self.name = name # Item changed event handler. def itemChanged(sender, eventArgs): # Obtain the custom object we have passed in. stateAsObject = eventArgs.Arguments.State if eventArgs.Succeeded: print(stateAsObject.name, ': ', eventArgs.Vtq, sep='') else: print(stateAsObject.name, ' *** Failure: ', eventArgs.ErrorMessageBrief, sep='') # Instantiate the client object. client = EasyDAClient() # Hook events. client.ItemChanged += itemChanged print('Subscribing item changes...') handleArray = IEasyDAClientExtension.SubscribeMultipleItems(client, [ DAItemGroupArguments('', 'OPCLabs.KitServer.2', 'Simulation.Random', 1000, CustomObject('First')), # a custom object that corresponds to the subscription DAItemGroupArguments('', 'OPCLabs.KitServer.2', 'Trends.Ramp (1 min)', 1000, CustomObject('Second')), # a custom object that corresponds to the subscription DAItemGroupArguments('', 'OPCLabs.KitServer.2', 'Trends.Sine (1 min)', 1000, CustomObject('Third')), # a custom object that corresponds to the subscription DAItemGroupArguments('', 'OPCLabs.KitServer.2', 'Simulation.Register_I4', 1000, CustomObject('Fourth')), # a custom object that corresponds to the subscription ]) for i in range(len(handleArray)): print('handleArray[', i, ']: ', handleArray[i], sep='') print('Processing item change notifications for 1 minute...') time.sleep(60) print('Unsubscribing all items...') client.UnsubscribeAllItems() client.ItemChanged -= itemChanged print('Finished.')
' This example shows how subscribe to changes of multiple items and display each change, identifying the different ' subscriptions by an object. ' ' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . Imports System.Threading Imports OpcLabs.EasyOpc.DataAccess Imports OpcLabs.EasyOpc.DataAccess.OperationModel Namespace DataAccess._EasyDAClient Partial Friend Class SubscribeMultipleItems Private Class CustomObject Sub New(name As String) Me.Name = name End Sub Public ReadOnly Property Name As String End Class Public Shared Sub StateAsObject() ' Instantiate the client object. Using client = New EasyDAClient() AddHandler client.ItemChanged, AddressOf client_StateAsObject_ItemChanged Console.WriteLine("Subscribing...") Dim handleArray() As Integer = client.SubscribeMultipleItems(New DAItemGroupArguments() { New DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Random", 1000, New CustomObject("First")), ' A custom object that corresponds to the subscription New DAItemGroupArguments("", "OPCLabs.KitServer.2", "Trends.Ramp (1 min)", 1000, New CustomObject("Second")), ' A custom object that corresponds to the subscription New DAItemGroupArguments("", "OPCLabs.KitServer.2", "Trends.Sine (1 min)", 1000, New CustomObject("Third")), ' A custom object that corresponds to the subscription New DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Register_I4", 1000, New CustomObject("Fourth")) ' A custom object that corresponds to the subscription }) For i As Integer = 0 To handleArray.Length - 1 Console.WriteLine($"handleArray[{i}]: {handleArray(i)}") Next i Console.WriteLine("Processing item changed events for 10 seconds...") Thread.Sleep(10 * 1000) Console.WriteLine("Unsubscribing...") End Using Console.WriteLine("Waiting for 5 seconds...") Thread.Sleep(5 * 1000) Console.WriteLine("Finished.") End Sub ' Item changed event handler Private Shared Sub client_StateAsObject_ItemChanged(ByVal sender As Object, ByVal eventArgs As EasyDAItemChangedEventArgs) ' Obtain the custom object we have passed in. Dim stateAsObject As CustomObject = CType(eventArgs.Arguments.State, CustomObject) If eventArgs.Succeeded Then Console.WriteLine($"{stateAsObject.Name}: {eventArgs.Vtq}") Else Console.WriteLine($"{stateAsObject.Name} *** Failure: {eventArgs.ErrorMessageBrief}") End If End Sub End Class End Namespace
// This example shows how to store current state of the subscribed items in a dictionary. // // Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . using System; using System.Collections.Generic; using System.Threading; using OpcLabs.EasyOpc.DataAccess; using OpcLabs.EasyOpc.DataAccess.OperationModel; namespace DocExamples.DataAccess._EasyDAClient { partial class SubscribeMultipleItems { public static void StoreInDictionary() { // Instantiate the client object. using (var client = new EasyDAClient()) { client.ItemChanged += client_ItemChanged_StoreInDictionary; Console.WriteLine("Subscribing item changes..."); client.SubscribeMultipleItems( new[] { new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Random", 1000, null), new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Trends.Ramp (1 min)", 1000, null), new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Trends.Sine (1 min)", 1000, null), new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Register_I4", 1000, null) }); Console.WriteLine("Processing item changed events for 1 minute..."); int startTickCount = Environment.TickCount; do { Thread.Sleep(5*1000); // Each 5 seconds, display the current state of the items we have subscribed to. lock (_serialize) { Console.WriteLine(); foreach (KeyValuePair<DAItemDescriptor, DAVtqResult> pair in _vtqResultDictionary) { DAItemDescriptor itemDescriptor = pair.Key; DAVtqResult vtqResult = pair.Value; Console.WriteLine($"{itemDescriptor}: {vtqResult}"); } // The code above shows how you can process the complete contents of the dictionary. In other // scenarios, you may want to access just a specific entry in the dictionary. You can achieve that // by indexing the dictionary by the item descriptor of the item you are interested in. } } while (Environment.TickCount < startTickCount + 60*1000); Console.WriteLine("Unsubscribing item changes..."); } Console.WriteLine("Finished."); } // Item changed event handler static void client_ItemChanged_StoreInDictionary(object sender, EasyDAItemChangedEventArgs e) { lock (_serialize) // Convert the event arguments to a DAVtq result object, and store it in the dictionary under the key which // is the item descriptor of the item this item changed event is for. _vtqResultDictionary[e.Arguments.ItemDescriptor] = (DAVtqResult)e; } // Holds last known state of each subscribed item. private static readonly Dictionary<DAItemDescriptor, DAVtqResult> _vtqResultDictionary = new Dictionary<DAItemDescriptor, DAVtqResult>(); // Synchronization object used to prevent simultaneous access to the dictionary. private static readonly object _serialize = new object(); } }
# This example shows how to store current state of the subscribed items in a dictionary. # # Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . # OPC client and subscriber examples in Python on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-Python . # The QuickOPC package is needed. Install it using "pip install opclabs_quickopc". import opclabs_quickopc import threading import time # Import .NET namespaces. from OpcLabs.EasyOpc.DataAccess import * from OpcLabs.EasyOpc.DataAccess.OperationModel import * lock = threading.Lock() vtqResultDictionary = {} # Item changed event handler. def itemChanged(sender, eventArgs): global lock global vtqResultDictionary with lock: # Convert the event arguments to a DAVtq result object, and store it in the dictionary under the key which # is the item descriptor of the item this item changed event is for. vtqResultDictionary[eventArgs.Arguments.ItemDescriptor] = EasyDAItemChangedEventArgs.ToDAVtqResult(eventArgs) # Instantiate the client object. client = EasyDAClient() # Hook events. client.ItemChanged += itemChanged print('Subscribing item changes...') handleArray = IEasyDAClientExtension.SubscribeMultipleItems(client, [ DAItemGroupArguments('', 'OPCLabs.KitServer.2', 'Simulation.Random', 1000, None), DAItemGroupArguments('', 'OPCLabs.KitServer.2', 'Trends.Ramp (1 min)', 1000, None), DAItemGroupArguments('', 'OPCLabs.KitServer.2', 'Trends.Sine (1 min)', 1000, None), DAItemGroupArguments('', 'OPCLabs.KitServer.2', 'Simulation.Register_I4', 1000, None), ]) for i in range(len(handleArray)): print('handleArray[', i, ']: ', handleArray[i], sep='') print('Processing item change notifications for 1 minute...') endTime = time.time() + 60 while time.time() < endTime: time.sleep(5) # # Each 5 seconds, display the current state of the items we have subscribed to. with lock: print() print('Current state of the items:') for itemDescriptor, vtqResult in vtqResultDictionary.items(): print(itemDescriptor, ': ', vtqResult, sep='') # # The code above shows how you can process the complete contents of the dictionary. In other # scenarios, you may want to access just a specific entry in the dictionary. You can achieve that # by indexing the dictionary by the item descriptor of the item you are interested in. print() print('Unsubscribing all items...') client.UnsubscribeAllItems() client.ItemChanged -= itemChanged print('Finished.')
' This example shows how to store current state of the subscribed items in a dictionary. ' ' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html . Imports System.Threading Imports OpcLabs.EasyOpc.DataAccess Imports OpcLabs.EasyOpc.DataAccess.OperationModel Namespace DataAccess._EasyDAClient Partial Friend Class SubscribeMultipleItems Public Shared Sub StoreInDictionary() ' Instantiate the client object. Using client = New EasyDAClient() AddHandler client.ItemChanged, AddressOf client_ItemChanged_StoreInDictionary Console.WriteLine("Subscribing item changes...") client.SubscribeMultipleItems(New DAItemGroupArguments() { New DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Random", 1000, Nothing), New DAItemGroupArguments("", "OPCLabs.KitServer.2", "Trends.Ramp (1 min)", 1000, Nothing), New DAItemGroupArguments("", "OPCLabs.KitServer.2", "Trends.Sine (1 min)", 1000, Nothing), New DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Register_I4", 1000, Nothing) }) Console.WriteLine("Processing item changed events for 1 minute...") Dim startTickCount As Integer = Environment.TickCount Do Thread.Sleep(5 * 1000) ' Each 5 seconds, display the current state of the items we have subscribed to. SyncLock _serialize Console.WriteLine() For Each pair As KeyValuePair(Of DAItemDescriptor, DAVtqResult) In _vtqResultDictionary Dim itemDescriptor As DAItemDescriptor = pair.Key Dim vtqResult = pair.Value Console.WriteLine($"{itemDescriptor}: {vtqResult}") Next ' The code above shows how you can process the complete contents of the dictionary. In other ' scenarios, you may want to access just a specific entry in the dictionary. You can achieve that ' by indexing the dictionary by the item descriptor of the item you are interested in. End SyncLock Loop While Environment.TickCount < startTickCount + 60 * 1000 Console.WriteLine("Unsubscribing item changes...") End Using Console.WriteLine("Finished.") End Sub ' Item changed event handler Private Shared Sub client_ItemChanged_StoreInDictionary(ByVal sender As Object, ByVal e As EasyDAItemChangedEventArgs) SyncLock _serialize ' Convert the event arguments to a DAVtq result object, and store it in the dictionary under the key which ' is the item descriptor of the item this item changed event is for. _vtqResultDictionary(e.Arguments.ItemDescriptor) = CType(e, DAVtqResult) End SyncLock End Sub ' Holds last known state of each subscribed item. Private Shared ReadOnly _vtqResultDictionary As New Dictionary(Of DAItemDescriptor, DAVtqResult) ' Synchronization object used to prevent simultaneous access to the dictionary. Private Shared ReadOnly _serialize As New Object End Class End Namespace
Requirements