MessageEventHandler delegate object is used to receive asynchronously delivered messages.
Each session must insure that it passes messages serially to the listener. This means that a listener assigned to one or more consumers of the same session can assume that the
onMessage method is not called with the next message until the session has completed the last call.
MessageEventArgsis the message passed to the listener
Assembly: WebLogic.Messaging (in WebLogic.Messaging.dll)