Microsoft® Windows® Communication Foundation Step by Step

Using a Callback Contract to Implement Events

One of the principal uses of a callback contract is to provide a service with a means to inform a client application of a significant occurrence. You can use callbacks to implement an eventing mechanism; the service can advertise events and provide operations to enable client applications to subscribe to these events or unsubscribe from them. The service can use the callback contract to send a message to each subscribing client when an event occurs. You will see how to do this later, but first you need to define, implement, and test a callback contract that can act as the basis for an eventing mechanism.

Add a callback contract to the ProductsService service and invoke a callback operation

1. Using Visual ...