Publish Message to Topic

The ITopic interface facilitates creating subscription and publishing of messages against the topic. This also provides event registrations for message delivery failure, receiving messages and deleting topics.

It provides the Publish method which publishes the message in the cache. It allows the user to specify the message delivery option using an enum DeliveryOption which has two options:

All (1): Delivers message to all the registered subscribers.
Any (0): Delivers the message to any one of the registered subscribers.

Moreover, it allows the publisher to get notified if the message has failed to deliver because of any issue using the notifyDeliveryFailure flag.

Pre-Requisites for Publishing Message

Include the following namespace in your application:
- Alachisoft.NCache.Web.Caching
- Alachisoft.NCache.Runtime

The application must be connected to cache before performing the operation.
Cache must be running.
Make sure that the data being added is serializable.
To ensure the operation is fail safe, it is recommended to handle any potential exceptions within your application, as explained in Handling Failures.

The following code sample does the following:

Create dedicated topics for Order related messages.
Register MessageDeliveryFailure event for topic.
Register OnTopicDeleted event for topic.
Create messages for each topic, enabling expiration and delivery options.
Publish the messages.

try
{
    // Pre-Condition: Cache is already connected

    // orderTopic is the name of the topic created beforehand
    string topicName = "orderTopic";

    // Get the topic 
    ITopic orderTopic = cache.MessagingService.GetTopic(topicName);
    if (orderTopic != null)
    {
        // Create the object to be sent in message
        Order order = FetchOrderFromDB(10248);

        // Create the new message with the object order
        Message orderMessage = new Message(order);

        // Set the expiration time of the message
        orderMessage.ExpirationTime = TimeSpan.FromSeconds(5000);

        // Register message delivery failure
        orderTopic.MessageDeliveryFailure += OnFailureMessageRecieved;

        //Register topic deletion notification
        orderTopic.OnTopicDeleted = TopicDeleted;

        // Publish the order with delivery option set as all
        // and register message delivery failure
        orderTopic.Publish(orderMessage, DeliveryOption.All, true);
    }
    else
    {
        // No topic exists
    }
}
catch (OperationFailedException ex)
{
    if (ex.Message.Contains("Topic 'orderTopic' is disposed."))
    {
        // orderTopic does not exist
    }
    else
    {
        // Exception can occur due to:
        // Connection Failures
        // Operation performed during state transfer
        // Operation Timeout
     }
}
catch (Exception ex)
{
    // Any other generic exception like ArgumentNullException or ArgumentException
}

Recommendation: To ensure the operation is fail safe, it is recommended to handle any potential exceptions within your application, as explained in Handling Failures.

Publish Message to Topic

See Also