When the binding extender is set to online (i.e. when its Online property is set to 'true'), following steps are performed internally:

1. Each configured binding makes its “links”, i.e. hooks the handlers for its configured event sources. For example, the PointBinding-s have ReadEventSource and WriteEventSource, so if they are configured, the binding will link the events with handlers that perform Read or Write operation on the point binding.
2. All binding groups perform their configured automatic operations. For  PointBindingGroup-s, this means that:
   1. If AutoRead property is set, the Read operation is executed for all PointBinding-s that have Read included in their BindingOperations property (this includes “Get” of OPC-DA properties).
   2. If AutoSubscribe property is set, the Subscribe(true) operation is executed for all PointBinding-s that have Subscribe included in their BindingOperations property.
3. All binding groups make their “links”, i.e. hook the handlers for their configured event sources. For PointBindingGroup-s, this means that the events for ReadEventSource and WriteEventSource will be linked with handlers that perform Read or Write operation on the binding group.
4. The OnlineChanged event is raised on the BindingExtender.

When setting the binding extender to offline, the above steps are (roughly said) reversed. There are, however, differences in Step 2: For PointBindingGroups-s, the Read operations are not executed; instead, if AutoWrite property is set, the Write operation is executed for all PointBinding-s that have Write included in their BindingOperations property. Also, if AutoSubscribe property is set, the Subscribe(false) operation is executed (i.e. unsubscribe, instead of subscribe).