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Canadian, I think you should call up the consulate first (at the phone numbers are on the previous post of mine) and find out who is permissible to enter into US with just an I-94 without a visa for that particular status or change of status thereof from Canada or Mexico. According to the current NAFTA rules, the ones who are permissible I had indicated in the previous post.
Canadian, the original post was "I changed from F-1 to H-1 in US. So, I have H-1 status and new I-94 card approved for H-1b at the same time, but no valid visa. I plan to visit Canada only for one day (possibly boring going and evening coming back.)" For your information the question cannot be answered until one know the follows: i. nationality; ii. status in Canada. In addition, one cannot enter back into US without a valid H-1B visa if the previous status was not H-1B. However, the individual can travel back with F-1 visa status. Yes, if the individual has Canadian PR then the individual can do a status change at the border/ airport (Preboarding Post) without going to Consulate.
By the way, granted that this outside the scope the question asked, however, additional information doesn\'t hurt. The objective of forums like these is exchange information not finger pointing each other... I could have also said to "do your homework" or I could have also said "People like you who does not much immigration laws about Canada and US usually try to confuse people. "