If specified, the OnClientRequestFailed client-side event handler is called when a request to the Web Service has failed.In the case of server-side binding, the event will not be raised.
Two parameters are passed to the handler:
sender - the scheduler client object;
eventArgs with two properties:
get_errorMessage() - the error message sent from the server.
set_cancel() - set to true to suppress the default action (alert message).
This event can be cancelled.