'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
// This example shows how subscribe to changes of multiple items and display each change, identifying the different // subscriptions by an integer. 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($"{stateAsInteger} *** Failure: {eventArgs.ErrorMessageBrief}"); } } }
// This example shows how subscribe to changes of multiple items and display each change, identifying the different // subscriptions by an object. using System; using System.Threading; using OpcLabs.EasyOpc.DataAccess; using OpcLabs.EasyOpc.DataAccess.OperationModel; namespace DocExamples.DataAccess._EasyDAClient { partial class SubscribeMultipleItems { class CustomObject { public CustomObject(string name) { Name = name; } public string Name { get; } } public static void StateAsObject() { // Instantiate the client object. using (var client = new EasyDAClient()) { // Hook events client.ItemChanged += client_StateAsObject_ItemChanged; Console.WriteLine("Subscribing..."); int[] handleArray = client.SubscribeMultipleItems(new[] { new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Random", 1000, new CustomObject("First")), // A custom object that corresponds to the subscription new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Trends.Ramp (1 min)", 1000, new CustomObject("Second")), // A custom object that corresponds to the subscription new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Trends.Sine (1 min)", 1000, new CustomObject("Third")), // A custom object that corresponds to the subscription new DAItemGroupArguments("", "OPCLabs.KitServer.2", "Simulation.Register_I4", 1000, new CustomObject("Fourth")) // A custom object that corresponds to the subscription }); for (int i = 0; i < handleArray.Length; i++) Console.WriteLine($"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}"); } } }
Requirements
Target Platforms: .NET Framework: Windows 10 (selected versions), Windows 11 (selected versions), Windows Server 2012, Windows Server 2016; .NET Core, .NET 5, .NET 6: Linux, macOS, Microsoft Windows
See Also