Connectivity Software User's Guide and Reference
SubscribeMonitoredItem(IEasyUAClient,EasyUAMonitoredItemArguments) Method



OpcLabs.EasyOpcUACore Assembly > OpcLabs.EasyOpc.UA Namespace > IEasyUAClientExtension Class > SubscribeMonitoredItem Method : SubscribeMonitoredItem(IEasyUAClient,EasyUAMonitoredItemArguments) Method
The client object that will perform the operation.

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

Array of arguments, one element per each monitored item involved in the operation.

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

Subscribe to changes of a particular monitored item. For each significant monitored item change, either the Subscribe to a monitored item, specifying an object that holds all necessary arguments (the object can optionally contain the callback method as well).
Syntax
'Declaration
 
<ExtensionAttribute()>
Public Overloads Shared Function SubscribeMonitoredItem( _
   ByVal client As IEasyUAClient, _
   ByVal monitoredItemArguments As EasyUAMonitoredItemArguments _
) As Integer
'Usage
 
Dim client As IEasyUAClient
Dim monitoredItemArguments As EasyUAMonitoredItemArguments
Dim value As Integer
 
value = IEasyUAClientExtension.SubscribeMonitoredItem(client, monitoredItemArguments)

Parameters

client
The client object that will perform the operation.

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

monitoredItemArguments
Array of arguments, one element per each monitored item involved in the operation.

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

Return Value

The method returns an integer handle that uniquely identifies the monitored item subscription.
Exceptions
ExceptionDescription

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

It is more efficient to subscribe to multiple monitored items using SubscribeMultipleMonitoredItems method.

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.

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