If you are off-shore, and want to get visa through the job you get in Canada, it is better to seek job opportunities through internet first then join a phone-call or video-call interview. But sometimes, in-shore company asks whether you have working permit in Canada or not.
But if you are talent in some areas or to say you are really good candidate, after rounds of interviews, company may help you apply visa (maybe work visa) so that they can hire you.