Will be called multiple times, once for each result. Although a callback, this is still invoked synchronously. That is, it is guaranteed that following a call to SyncApiOp.Sync(ObjectClass, SyncToken, SyncResultsHandler, OperationOptions) no more invocations to Handle(SyncDelta) will be performed.
If the application encounters an exception. This will stop
/// the interation and the exception will be propogated back to
/// the application.