QuickOPC User's Guide and Reference
SubscribeMonitoredItem Method



OpcLabs.EasyOpcUA Assembly > OpcLabs.EasyOpc.UA Namespace > IEasyUAClientExtension Class : SubscribeMonitoredItem Method
Subscribe to changes of a particular monitored item. For each significant monitored item change, either the IEasyUAClient.DataChangeNotification event is generated, or a specified callback method is invoked.

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

Overload List
OverloadDescription
Subscribe to changes of a particular monitored item. For each significant monitored item change, either the IEasyUAClient.DataChangeNotification event is generated, or a specified callback method is invoked. Subscribe to a monitored item, specifying an object that holds all necessary arguments (the object can optionally contain the callback method as well).  
Subscribe to changes of a particular monitored item. For each significant monitored item change, either the IEasyUAClient.DataChangeNotification event is generated, or a specified callback method is invoked. Subscribe to a monitored item, specifying an object that holds all necessary arguments, and a data change callback method.  
Subscribe to changes of a particular monitored item. For each significant monitored item change, either the IEasyUAClient.DataChangeNotification event is generated, or a specified callback method is invoked. Subscribe to a monitored item, specifying an object that holds all necessary arguments, and an event callback method.  
Remarks

 

This method operates (at least in part) asynchronously, with respect to the caller. The actual execution of the operation may be delayed, and the outcome of the operation (if any) is provided to the calling code using an event notification, callback, or other means explained in the text. In a properly written program, this method does not throw any exceptions. You should therefore not put try/catch statements or similar constructs around calls to this method. The only exceptions thrown by this method are for usage errors, i.e. when your code violates the usage contract of the method, such as passing in invalid arguments or calling the method when the state of the object does not allow it. Any operation-related errors (i.e. errors that depend on external conditions that your code cannot reliably check) are indicated by the means the operation returns its outcome (if any), which is described in the text. For more information, see Do not catch any exceptions with asynchronous or multiple-operation methods.
Requirements

Target Platforms: .NET Framework: Windows 10, Windows Server 2012, Windows Server 2016; .NET Core, .NET 5: Linux, macOS, Microsoft Windows

See Also

Reference

IEasyUAClientExtension Class
IEasyUAClientExtension Members