Universal Messaging Developer Guide : Enterprise APIs : Enterprise Developer's Guide for C# : Publish / Subscribe using Channel Topics : Subscribe Asynchronously to a Channel
Subscribe Asynchronously to a Channel
Asynchronous channel subscribers consume events from a callback on an interface that all asynchronous subscribers must implement. We call this interface an nEventListener.
The listener interface defines one method called 'go' which when called will pass events to the consumer as they are delivered from the Universal Messaging Realm Server.
A simple example of such a listener is shown below:

public class mySubscriber : nEventListener {

public mySubscriber() {
// construct your session and channel objects here
// begin consuming events from the beginning of the channel (event id 0)
myChannel.addSubscriber(this, 0);
}

public void go(nConsumeEvent event) {
Console.WriteLine("Consumed event " + event.getEventID());
}

public static void Main(String[] args) {
new mySubscriber();
}

}
Subscription with a Filtering Selector
Asynchronous consumers can also be created using a selector, which allows the subscription to be filtered based on event properties and their values.
For example, assume some events are being published with the following event properties:

nEventProperteis props = new nEventProperties();
props.put("BONDNAME", "bond1");
A developer can create a message selector string such as:

String selector = "BONDNAME='bond1'";
Passing this string into the addSubscriber method shown in the example code, will ensure that the subscriber will only consume messages that contain the correct value for the event property BONDNAME.
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