Cache Level Events

By default, cache level events are disabled (except for Cache Cleared) for any cache configuration and must be enabled for events to be published.

Cache Level Notifications are fired when data is added in cache from clients, loader, read-through etc.

Cache Level Data Notifications can be used to share data across different clients, the purpose of this feature is to notify clients about every operation performed on cache [add, insert, remove].

Clients that want to receive these notifications will have to register Cache Level Notification through API calls.

Note

The application will not be able to receive events unless it registers itself against cache using the specific event registration API call.

Registering Cache Level Events

To utilize the API, include the following namespace in your application: Alachisoft.NCache.Web.Caching.

Cache Level notifications are generic events which will be triggered upon every execution of the appropriate registered event type. To register these events for notification, RegisterCacheNotification method is used.

Appropriate EventType to be registered needs to be specified; single as well as multiple event types can be specified in a single method call. Also, EventDataFilter needs to be specified to quantify the amount of information returned upon an event execution.

Warning

EventDataFilter must be carefully set to avoid unnecessary network bandwidth consumption.

// Create a target method
public static void OnCacheDataModification(string key, CacheEventArg args)
{
    switch (args.EventType)
    {
      case EventType.ItemAdded:
      //perform appropriate operations
      break;
      case EventType.ItemRemoved:
      //perform appropriate operations
      break;
      case EventType.ItemUpdated:
      //perform appropriate operations
      break;
    }
}

// Register target method
CacheDataNotificationCallback dataNotificationCallback = new CacheDataNotificationCallback(OnCacheDataModification);
try
{
    // Register cache notification with appropriate event type
    CacheEventDescriptor EventDescriptor = cache.RegisterCacheNotification(dataNotificationCallback,
    EventType.ItemAdded | EventType.ItemRemoved | EventType.ItemUpdated,
    EventDataFilter.None);
    // Save the event descriptor for further usage
}
catch (Exception ex)
{
    // handle exception
}

The events will be notified to their appropriate listeners and handled as implemented by the user.

Un-registering Cache Level Events

A previously registered cache level notification can also be unregistered using the UnRegisterCacheNotification method. In this example, the EventDescriptor previously returned upon registering of event, needs to be specified.

try
{
    cache.UnRegisterCacheNotification(EventDescriptor);
}
catch (Exception ex)
{
    // handle exception
}