/// <summary>
/// Subscribes to events.
/// </summary>
/// <param name="context">The context.</param>
/// <param name="source">The source.</param>
/// <param name="monitoredItem">The monitored item.</param>
/// <param name="unsubscribe">if set to <c>true</c> [unsubscribe].</param>
/// <returns>Any error code.</returns>
protected virtual ServiceResult SubscribeToEvents(
ServerSystemContext context,
NodeState source,
IEventMonitoredItem monitoredItem,
bool unsubscribe)
{
MonitoredNode monitoredNode = null;
// handle unsubscribe.
if (unsubscribe)
{
// check for existing monitored node.
if (!MonitoredNodes.TryGetValue(source.NodeId, out monitoredNode))
{
return StatusCodes.BadNodeIdUnknown;
}
monitoredNode.Remove(monitoredItem);
// check if node is no longer being monitored.
if (!monitoredNode.HasMonitoredItems)
{
MonitoredNodes.Remove(source.NodeId);
}
// update flag.
source.SetAreEventsMonitored(context, !unsubscribe, true);
// call subclass.
OnSubscribeToEvents(context, monitoredNode, unsubscribe);
// all done.
return ServiceResult.Good;
}
// only objects or views can be subscribed to.
BaseObjectState instance = source as BaseObjectState;
if (instance == null || (instance.EventNotifier & EventNotifiers.SubscribeToEvents) == 0)
{
ViewState view = source as ViewState;
if (view == null || (view.EventNotifier & EventNotifiers.SubscribeToEvents) == 0)
{
return StatusCodes.BadNotSupported;
}
}
// check for existing monitored node.
if (!MonitoredNodes.TryGetValue(source.NodeId, out monitoredNode))
{
MonitoredNodes[source.NodeId] = monitoredNode = new MonitoredNode(this, source);
}
// this links the node to specified monitored item and ensures all events
// reported by the node are added to the monitored item's queue.
monitoredNode.Add(monitoredItem);
// This call recursively updates a reference count all nodes in the notifier
// hierarchy below the area. Sources with a reference count of 0 do not have
// any active subscriptions so they do not need to report events.
source.SetAreEventsMonitored(context, !unsubscribe, true);
// signal update.
OnSubscribeToEvents(context, monitoredNode, unsubscribe);
// all done.
return ServiceResult.Good;
}
/// <summary>
/// Subscribes to events.
/// </summary>
/// <param name="context">The context.</param>
/// <param name="source">The source.</param>
/// <param name="monitoredItem">The monitored item.</param>
/// <param name="unsubscribe">if set to <c>true</c> [unsubscribe].</param>
/// <returns>Any error code.</returns>
protected override ServiceResult SubscribeToEvents(
ServerSystemContext context,
NodeState source,
IEventMonitoredItem monitoredItem,
bool unsubscribe)
{
// handle unsubscribe.
if (unsubscribe)
{
// check for existing monitored node.
if (!MonitoredNodes.TryGetValue(source.NodeId, out MonitoredNode2 monitoredNode2))
{
return(StatusCodes.BadNodeIdUnknown);
}
monitoredNode2.Remove(monitoredItem);
// check if node is no longer being monitored.
if (!monitoredNode2.HasMonitoredItems)
{
MonitoredNodes.Remove(source.NodeId);
}
// update flag.
source.SetAreEventsMonitored(context, !unsubscribe, true);
// call subclass.
OnSubscribeToEvents(context, monitoredNode2, unsubscribe);
// all done.
return(ServiceResult.Good);
}
// only objects or views can be subscribed to.
BaseObjectState instance = source as BaseObjectState;
if (instance == null || (instance.EventNotifier & EventNotifiers.SubscribeToEvents) == 0)
{
ViewState view = source as ViewState;
if (view == null || (view.EventNotifier & EventNotifiers.SubscribeToEvents) == 0)
{
return(StatusCodes.BadNotSupported);
}
}
// check for existing monitored node.
if (!MonitoredNodes.TryGetValue(source.NodeId, out MonitoredNode2 monitoredNode))
{
MonitoredNodes[source.NodeId] = monitoredNode = new MonitoredNode2(this, source);
}
// this links the node to specified monitored item and ensures all events
// reported by the node are added to the monitored item's queue.
monitoredNode.Add(monitoredItem);
// This call recursively updates a reference count all nodes in the notifier
// hierarchy below the area. Sources with a reference count of 0 do not have
// any active subscriptions so they do not need to report events.
source.SetAreEventsMonitored(context, !unsubscribe, true);
// signal update.
OnSubscribeToEvents(context, monitoredNode, unsubscribe);
// all done.
return(ServiceResult.Good);
}
